Unlike other tech companies that rush out new products without rhyme or reason--Quick! Samsung just put out another smartwatch while I was typing this sentence!--Apple takes its sweet time with releases, particularly when it comes to mobile devices. We've made an entire circuit around the sun since the last time Tim Cook waved new iPhones in the air, which has given other smartphone makers plenty of time to match and even surpass what the iPhone 5s brings to the table.

Not that Apple loses much sleep over that--at least not anyone who isn't on Apple's legal team. Since it first unveiled the iPhone more than seven years ago, the company seems more concerned with setting the bar in the smartphone market than in matching someone else's phone feature for feature.

Follow all of Apple's September 9 announcements in our live coverage of Tuesday's big event

Still, a lot's changed for smartphones since the last time Apple has overhauled its product line. And it's worth taking note of a few of the major trends at play in the market that the iPhone 6--or whatever Apple winds up calling it--will enter.

Cameras have added more tricks

What Apple did: The iPhone's never been big on upping the megapixel count--the iPhone 5s's rear-facing camera clocks in at a relatively modest 8 megapixels. Instead, last year's phone put the emphasis on software, adding a Slo-Mo mode that shoots 720p HD video at 120 frames per second and a burst mode for taking 10 full-quality photos in a second.

What's happened since: Other smartphones continue to push the megapixel count on their built-in cameras, particularly if they're hoping to use photo features to stand out from the crowd. The Nokia Lumia 930, for example, boasts a 20-megapixel camera, while Samsung's Galaxy S5 and LG's G3 offer cameras touting 16 and 13 megapixels, respectively. But even these smartphones seem to recognize there's more to life than just megapixels. The Nokia 930 ships with a bunch of photo-editing apps including one that lets you edit high-resolution photos right on the phone; meanwhile, LG simplified the camera interface on the G3, stripping out a lot of the control options to put the emphasis on snapping photos.

Like the iPhone 5s, HTC's One (M8) doesn't pack in the megapixels, but it does offer two rear-facing cameras, which it uses for post-processing tricks, such as creating depth-of-field effects on your images.

Other phone makers have realized there's advances to be made with the front-facing camera, particularly as our national obsession with self-portraits continues unabated. HTC's flagship phone offers a Selfie mode, complete with a three-second countdown, and the front-facing camera on the just-announced Galaxy Note 4 from Samsung features an f1.9 wide-angle lens designed for taking better self-portraits.

What Apple might do next: Past iPhone updates have introduced improvements to both the camera's hardware and software. It's hard to imagine a new iPhone not following suit, with a more powerful sensor and some editing tricks along the lines of what the company introduced with the 5s. The front-facing camera--long the laggard in the iPhone's photo arsenal--could stand some selfie-inspired improvements as well.

Phones have gotten bigger

What Apple did: The iPhone 5s retained the dimensions of its predecessor, right down to its 4-inch screen. (The iPhone 5c was slightly taller, wider, and thicker and weighed 0.7 ounces more, but it also featured a 4-inch display.) Prior to the iPhone 5's 2012 release, iPhones featured a 3.5-inch screen.

What's happened since: While Apple has held the line on how big phones should be, other device makers haven't shied away from super-sizing their products. The HTC One offers a 5-inch screen; the Galaxy S5's screen checks in at 5.1 inches. And those screens are positively cramped compared to the 5.5- and 5.7-inch screens you'll find on the LG G3 and Galaxy Note 4, respectively. These are not outliers--NPD Group says that large-screen smartphones (ones with screens 4.7 inches or larger) now take up a third of the shelf space for national carriers; that's up from 4 percent just two years ago. Those large smartphones also make up more than a quarter of sales, up from 2 percent in the second quarter of 2012. (Interestingly, NPD says that sales figures are lagging, in part because Apple and its smaller-screened phones continue to enjoy a large slice of the smartphone market.)

What Apple might do next: Rumors point to Apple coming out with different sizes of its next iPhone at Tuesday's press event, though given Apple's reluctance to come out with a product just because everyone else is doing it, expect that any iPhone with a larger screen will have a very specific purpose for sporting one.

Displays have packed in more pixels

What Apple did: The iPhone 4 introduced the world to the Retina Display, and it was an eye-popping experience. Packing in 326 pixels per inch onto your phone's screen, Apple's high-resolution display made on-screen text look like something off a printed page. Apple's wisely stuck with the feature through subsequent iPhone iterations: the 5s offers 1136-by-640-pixel resolution with that same 326 pixels per inch (ppi).

What's happened since: Other phone makers have responded by packing in more pixels. The Galaxy S5 boasts a resolution of 1080-by-1920 with a pixel density of 432 ppi while the HTC One (M8) boasts 441 ppi on a scree with the same resolution. That's nothing compared to the Quad HD display on LG's G3: it features a resolution of 2560-by-1440 and 534 pixels per inch.

Would you even notice that many pixels during day-to-day use? It's unlikely that you would. Really, at a certain point, on screens designed to fit into your pocket, there's only so many pixels per inch you're going to be able to spot. With most high-end smartphones offering high-resolution screens, this seems like less of a selling point going forward. Size and brightness--and how those things affect battery life--seem like more pressing concerns.

If there's a phone doing something unique with its display, it's Amazon's Fire Phone (which is not exactly selling like hotcakes. The Fire Phone features a display with Dynamic Perspective, where the phone adjusts what's on the screen to reflect where you're looking. (Rotate your head in the Fire Phone's Maps app, for example, and you can get a close-up view of some 3D landmarks.)

What Apple might do: If Apple does wind up producing larger phones, it's also going to have to come up with enough power (most likely via a higher-capacity battery) to let that screen shine in all its Retina Display glory.

Phone makers are eyeing durability

What Apple did: Touting how its phones stand up to the rigors of daily use has never really been a part of Apple's sales pitch when it takes the wraps off new phones. (For that, you can do a web search to see people inflicting all sorts of damage on their iPhones in the name of science.) While Apple generally keeps a tight lid on who supplies the parts for its devices, it's widely assumed the company uses Gorilla Glass, the glass cover from Corning that helps resist scratches, as part of the iPhone's screen.

What's happened since: With smartphones becoming a more essential part of people's lives, phone makers have turned to durability as a possible selling point for their devices. That's certainly been the tack adopted by Sony with its Xperia line of smartphones: the latest version, the Xperia Z2 can be submerged in up to 5 feet of water for half-an-hour without suffering any damage.

What Apple might do: Apple's relationship with industrial sapphire maker GT Advanced Technology--the two companies have teamed up on a sapphire crystal plant in Mesa, Arizona--has led some (OK, me) to speculate that Apple's next smartphone will incorporate sapphire--the hardest natural substance after diamond--into its screen. If Apple does that (without driving up the cost of its phone), durability could become a larger part of the iPhone's story.

You can do more with your finger

What Apple did: Arguably the biggest addition to last year's iPhone 5s was its TouchID fingerprint sensor. The feature lets you unlock your phone with just a touch of a recognized fingerprint. It's not a bullet-proof security measure by any means, but it certainly makes it easier--and a little bit cooler--to unlock your phone.

What's happened since: Samsung followed suit with a fingerprint scanner of its own in the Galaxy S5. It's not a particularly good implementation, but Samsung did advance the ball a little bit by allowing participating apps to tap into the fingerprint scanner. That's something you couldn't do with an iPhone (at least, not yet).

Samsung also figured out other ways to put your fingers to work with the S5. It added an integrated heart motion onto the back of the phone: place an index finger on the sensor with the included S Health app running, and you can measure your beats per minute. There are some implementation issues (not the least of which is, the super-sized Galaxy S5 isn't the most compact exercise companion), but it's an advance that reduces the need for a separate fitness tracker.

What Apple might do: Remember how I said you couldn't use the TouchID sensor with other apps? That's going to change with iOS 8, which will allow apps to unlock themselves with the touch of a verified fingerprint. iOS 8 also features a new app called Health, powered by a set of tools called HealthKit that will collect your personal health data. HealthKit is designed to work with connected medical devices, which could include Apple's rumored smartwatch... or even a new iPhone.