So I usually read these threads and don't participate much, but this time I feel compelled. I read the first 4 pages and the last pages, so apologies in advance if this has been said before.
I'm all fine with the current level of "thinness", no need to go any thinner - keep it the same and give me more battery life as the internals shrink. What I'm not OK with is holes in my iPhone. You know - the things that let water and dirt in, and found surrounded by scratch marks where the connectors go in and out. I'm beside myself with amazement that in 2015 a $750 piece of tech is an instant brick when it falls in water. All holes need to die!
The technology exists already to inductively charge the phone, and your headsets and many other things. They will admittedly take longer to charge, but the advancement of technology will make that much better. You could have the equivalent of a small connector that functions similar to a magsafe connector for most things that require energy to run (if local battery usage is impractical). WiFi or cellular syncing is doable and constantly getting better. The energy loss in the phone transferring power to earphones will mean a hit in the maximum duration for music-only listening, but if the thinness is maintained the extra battery you get would compensate. The main drain in a phone is still all the radio/WiFi/communications related stuff. You can still keep your 3.5mm equipped headphones, but you would need one (inductively coupled) adapter to compensate. Full disclosure - I'm an electronics engineer that works for a company that has been known to supply components to Apple from time time time, although the topic of this thread has nothing to do with any existing or future products that I know of.
I want my next iPhone to be a fully sealed, waterproof, dust proof, goof proof and forgiving appliance. I'm so done with treating my phone like a newborn baby every time I go to use it. Anyway, it's probably time for my bashing now (which is why I usually never participate in these threads)...