The Apple Watch Series 3 was unveiled on 12 Sept 2017, and hit the shops 10 days later. But we're already looking ahead to Apple's next trick: when will the Series 4 be released, and what new features and tech specs should we expect?

In this article we sift through the evidence and predict what new features and technologies the Series 4 will offer, as well as discussing what we would like to see next.

Release date

Three generations in, we're starting to get a feel for Apple's smartwatch launch schedule, which was irregular early on but appears to be settling down into an annual event.

These are onsale launch dates; the first model in particular was announced a long time ahead of this.

It's early days but our money is on an update in autumn 2018, and most likely in September alongside new iPhones.

There has been a separate rumour that Apple could release a between-full-updates 'S' edition of the Apple Watch: presumably a Series 3S. This would add extra storage options the Series 3 and come out before the Series 4.

Design

Apple's pretty much kept the same design for three generations in a row (aside from some minor cosmetic tweaks, such as a new material and colour options, and a red spot on the cellular model). Having broken a significant boundary when adding the cellular connectivity feature in 2017, we think the company may focus instead on an all-new design in 2018.

The longest Apple has kept the same broad design in its iPhone line-up, as a comparison, is three generations, from the iPhone 6 to the iPhone 8 - and the iPhone X ended that sequence a month later. Apple may feel that the watch sector is more aesthetically conservative than the phone one, but it would still be a surprise to us if they broke their record and had four essentially identical smartwatches on the spin.

Round face

But what would a reimagined Apple Watch look like? The circular-face rumour will inevitably reappear, but we've never liked the way that affects the interface on Android Wear watches (text gets squeezed at top and bottom, and usually ends up unattractively centre-justified). Apple's interface control-freakery would probably preclude its catering for square and circular screens with the same OS.

Indeed, we would never have considered the round-face concept possible had we not seen the following drawing in a patent:

Apple Watch Series 4 release date, specs & price rumours: Patent

That patent is actually related to a strap design technology, which we will discuss below, and it could be round because Apple uses generic images for its patent designs to ensure a broad scope: this doesn't necessarily mean a round design is being seriously considered.

There are many Android Wear smartwatches that have round faces now making us wonder if people really do prefer circles. Smartwatches like the Huawei Watch 2, Moto 360 2 and LG G Watch R look like traditional watches with completely digital, circular displays and are extremely popular. (Read our comparison of the Apple Watch 2 and Huawei Watch 2 here).

Apple Watch Series 4 release date, specs & price rumours: Huawei Watch screen issues

Modular straps or smart bands

This is one of the more prominent rumours we're hearing. The idea is that Apple is considering producing new multi-function smart bands that it will sell with the Watch.

By moving some of the technologies from inside the watch face and into these smart bands Apple would be able to add new features without being as limited by the small size of the Watch face. This would enable Apple to add such features as a camera, or a bigger battery.

A number of patents have appeared suggesting that Apple has been working on this idea for some time. For example, a patent, originally filed in 2015, shows off a design for a band with its own battery.

The band could also house other components in a modular design, with each link performing a separate function. Users would be able to swap out modules depending on their requirements.

Another patent surfaced in May 2017 and was also filed in 2015. That patent is for "Display Module and System Applications", discovered by Patently Apple, shows an Apple Watch with a continuous display running from the watch face through the band. In the description that accompanies the image the patent states: "A flexible display panel #215, #315 (noted above) may be integrated into the smartwatch so that it spans both the watch face and band." This suggests that the watch face could extend into the band.

Apple Watch Series 4 release date, specs & price rumours: Patent

The patent also describes how a "module within the watch includes a processor and memory" and may also include a module to "communicate with a wide area network including a cellular data network".

Modular strap could also be useful for health monitoring.

Back in 2015, Cook said that while Apple had a keen interest in health-focused products, it decided against adding sensors to the watch because of concerns about FDA approval, which "would hold [Apple] back from innovating too much, the cycles are too long"; although Cook hinted at an accessory or app that could sit alongside it.

"But you can begin to envision other things that might be adjacent to it," he teased. "Maybe an app, maybe something else."

An interchangeable smart band would allow Apple to add health features to the Apple Watch. One area that the company is said to be interested in developing is glucose monitoring, and this could be offered via one of these smart bands. Smart bands should allow Apple to avoid submitting the watch for FDA approval: instead, only the band would need approval.

So perhaps an Apple Watch of the future could move some components into the strap, freeing up the watch face for other technologies.

Thinner & lighter

One of the bonuses of the modular bands described above is that it could free up the watch face, enabling Apple to make that thinner and lighter. (On the other hand, the whole watch could end up heavier if you include the pimped-up strap.)

New display design

Some illustrations in an Apple patent for "Display Module and System Applications," published in May 2017 by the US Patent and Trademark Office and discovered by Patently Apple, show what looks like it could be a new design for the Apple Watch. If you'd like to have an Apple Watch with a continuous display running from the face through the band, you might be pleased.

Apple Watch Series 4 release date, specs & price rumours: Patent

New wristband design

There are also patents that relate to the design of the wrist band: first spotted by AppleInsider in 2016, Apple has filed a patent for a Magnetic Wristband. The patent details a wristband for the Apple Watch that would feature a set of magnets embedded into it, allowing the two sides to join together.

For consumers, this means that when worn, the magnets would hold the Apple Watch in place (much like Apple's Milanese Loop) - but it's when the watch is taken off that the new band comes into its own.

Apple Watch Series 4 release date, specs & price rumours: Patent

The strap could be wrapped around the watch, which would suspend the screen in the middle of the straps: ideal for protection when being stored or transported. As well as offering additional protection, the strap could also double up as a stand (ideal for Apple's nightstand mode) as it's been designed to roll up behind the watch, propping it up.

Apple Watch Series 4 release date, specs & price rumours: Patent

Related: Apple Watch accessories round-up | Best Apple Watch straps

New features

Now you've got a good idea of what the third-generation Apple Watch will look like, we'll look at possible Apple Watch Series 4 hardware features.

Built-in camera

The current Apple Watch can be used as a camera viewfinder so that you can take a remote photograph with your iPhone, but it can't actually take photos itself or make video calls. However, if the rumours about the modular straps are correct, a camera could find its way into the Apple Watch soon.

Apple has patents for a wearable device that features a front-facing camera. It was rumoured to appear in the Series 2 and 3, but the feature wasn't announced. It's likely we could see this feature being included in the next iteration.

Opinions differ on whether this is intended to cater for FaceTime or selfies (or both), and whether it will offer video or just stills photography. The new camera would be integrated into the top bezel of the watch.

This feature does sound interesting, though we're not too sure how many people would actively FaceTime via a watch. It would be painful holding up the wrist for more than a few minutes, for one thing.

Still, Apple has already made its watch partially FaceTime-ready: watchOS 2 brought support for FaceTime audio calls. Does that indicate that it'll soon move on to video calls? Perhaps.

Patently Apple, meanwhile, has spotted an Apple patent that appears to support the inclusion of a selfie camera - a front-facing stills camera, in other words; not necessarily one that's capable of FaceTime video - in an Apple Watch in the future.

Apple Watch Series 4 release date, specs & price rumours: Selfie camera

Patent 20160174025, which pertains in seemingly broad terms to methods for 'facilitating access to location-specific information using wireless devices', but actually focuses on wearables, contains a reference to digital photography and its use "to capture images of the user". Also see: How to write apps for the Apple Watch.

Apple Watch Series 4 release date, specs & price rumours: Selfie camera

Better battery life

Calls for the Apple Watch battery to improve were answered with the release of the Apple Watch Series 2, which features a battery that should last two days between charges (the original Apple Watch needed charging every day).

Apple Watch Series 4 release date, specs & price rumours: Battery Image credit: iFixit

Better battery life also opens up more functionality in the Apple Watch, mainly with regards to sleep tracking. One problem with the Apple Watch battery is that the necessity of charging it at night means that people can't use it for sleep tracking. With a longer battery life, users could wear the Apple Watch to bed and get accurate stats about their sleep - information that's pretty popular, judging by the success of sleep-tracking apps such as Sleep Cycle.

Fortunately, it looks like Apple may be taking note. According to Economic Daily News Apple's focus with the Watch 3 is battery life, as per a January 2017 report on 9to5Mac.

Related: How to improve the Apple Watch's battery life and Best Apple Watch charging docks

New health sensors

Ahead of its original launch back in April 2015, there was a lot of talk regarding Apple's plans for the wearable and specifically that it'd be loaded with health sensors. So far that's not proven to be the case, with heart-rate and activity tracking offering a standard level of fitness tracking, but nothing more. There were reports at the time of launch suggesting that the sensors available at the time just weren't accurate enough - and no risks can be taken when it comes to health monitoring.

In an interview with The Telegraph in November 2015, Tim Cook hinted that the company may make a medically approved device, but it wouldn't be the Apple Watch. Cook explained that the disruption that FDA accreditation would cause to the product release cycle ultimately put him off having the Apple Watch vetted for full-blown health use. Although with this being said, it hasn't completely put him off the idea of building a product for use in the medical world:

"We don't want to put the watch through the Food and Drug Administration (FDA) process. I wouldn't mind putting something adjacent to the watch through it, but not the watch, because it would hold us back from innovating too much, the cycles are too long. But you can begin to envision other things that might be adjacent to it - maybe an app, maybe something else."

As we discussed earlier in this piece, the company may have found a way around the need for FDA approval, by placing these health related sensors in interchangeable straps that can be worn with the Watch.

Apple Watch Series 4 release date, specs & price rumours: Health

There company is certainly showing interest in health. In December 2015 and January 2016, Apple posted two listings looking for biomedical engineers with a background in "medical, health, wellness and/or fitness sensors, devices and applications". Although there is no mention of the Apple Watch in the listings, it's widely assumed that the roles are related to the listing for a fitness software engineering manager, which went up in November and is specifically for the Apple Watch.

BuzzFeed News also reported that over the last three months, Apple has stolen employees from all over the medical field. An example given by the news outlet is Anne Shelchuk, who has a doctorate in biomedical engineering. Shelchuk left the ultrasound software company ZONARE Medical Systems back in November to work with Apple's health technology team, according to her LinkedIn.

Along with Shelchuk, Apple has reportedly snapped up medical engineer Craig Slyfield, system design engineer Nathan Clark, who has a patent for a device that separates cells, Jay Mung, who worked on sensor algorithms for Medtronic's continuous glucose monitoring systems and Jennifer Hillier, a former exercise physiologist at the University of California.

The company is said to have been investigating ways in which the watch would be able to "non-invasively monitoring blood glucose", according to a CNBC report, and the company is said to have hired 200 health PhDs to help it innovate in this area. Reports suggest that the next Apple Watch could offer blood sugar monitoring.

Software

Whatever design and features the third-generation Apple Watch sports, we assume it'll boast watchOS 5. According to the usual schedule this will be announced at WWDC 2018 in June of that year, and released the following autumn.

watchOS 5 will bring a range of new features and interface tweaks to the Apple Watch. These will be optimised to run best on the new Series 4 hardware, but owners of most or perhaps even all Apple Watch models will be able to upgrade and get the new features for free. This may not be the best of ideas in some case, since our original model has slowed down noticeably since upgrading to watchOS 4 and even our Series 2 is not what it used to be.

Tech specs

It's very early to speculate about the Series 4's innards, but we've heard one credible rumour already:

Liquid crystal polymer antenna

Ming-Chi Kuo has published a report predicting that the liquid crystal polymer (LCP) circuit board tech currently used in the iPhone X and iPhone 8 will be rolled out across the Mac and Apple Watch ranges. In the case of the next watch this will be used in the cellular antenna.

LCP is more resistant to heat and moisture than other technologies, but when used in the antenna it adds the benefits of a more stable frequency signal transmission.

UK price

At time of writing, the Apple Watch Series 3 starts at £399 (with cellular) or £329 (without) in the UK; in the US the equivalent figures are the same, only in dollars.

Depending on how radically Apple rethinks the Series 4, we'd expect pricing to remain the same or almost the same when the new models are released; any previous-generation watches that remain on sale will get a juicy price cut.

You might not have to pay full price for the Apple Watch - here are some Apple Watch deals and our Apple Watch buying guide so you can avoid paying more than you need to.