Jon Prosser - the YouTube presenter and well-connected leaker whose every pronouncement we now hang on, since he correctly predicted the iPhone SE - says an iPhone with no ports at all is in the works, and will be launched next year.
That means it won't be ready in time for the iPhone 12 launch in autumn 2020, a launch that we expect to focus mainly on 5G. It will also bring two new screen sizes and various other changes, but nothing as drastic as the loss of all physical ports. Nope, the portless design won't be with us until autumn 2021.
If the iPhone 13 has no ports - Prosser says Apple will skip the USB-C phase entirely, at least on its iPhones - you won't be able to charge or connect headphones via Lightning; instead you'll have to charge and play audio wirelessly, which many people do already. But those who shelled out for expensive Lightning headphones in particular are likely to be cheesed off by having that option removed.
What are the benefits of an entirely portless design? Normally we'd say 'water resistance', since it means there aren't physical apertures through which liquid can invade the device's cavity. But the iPhone 11 Pro is already IP68, the highest IP rating given to consumer products, and is certified as able to withstand a depth of 4m for up to 30 minutes. It's hard to see how much further Apple could push things with the benefit of a portless design.
A bigger factor - and you'd want to get some substantial benefit, given that some people will be annoyed to lose the option of faster wired charging and more reliable/higher quality wired audio - is that Apple's engineers and designers will have more wiggle room when devising the device's internal layout. A Lightning port obviously isn't just a hole in the bottom of your phone: it has a bunch of components connected to it, and those components have to line up exactly with the aperture.
Lose the port and you can rearrange the internals, and fill the space with, say, a larger battery cell or more storage. Or make the whole thing slimmer.
This ignores, of course, the most Apple reason of all, which is that any kind of physical port (or button, for that matter) is an imperfection that should be removed as soon as it is practical to do so. The minimalist designer's Platonic ideal is a completely featureless white cube.