Since the upcoming phone after the iPhone 5 will be the iPhone 5s, it will physically look exactly the same as the iPhone 5. As with the upgrade from the iPhone 4 to the iPhone 4S, there will of course be the obvious upgrade in processor/GPU package, maybe the memory, NFC, and perhaps even upgrades to the camera. iOS 7 will probably include upgrades to Siri, maybe more upgrades to the maps app, some new APIs, and maybe some additions to make the device more enterprise friendly. Those upgrades are obvious and not very exciting. I would however, seriously consider the following new features never before seen in a smartphone.
1. Lithium-titanate battery. Imagine being able to charge your battery to 90% in 10 minutes. That's what lithium-titanate batteries offer. At the moment, production of these batteries are cost prohibitive, but with Apple's buying power, it might be possible to achieve sufficient economies of scale to make these batteries available for consumer electronics. For now, these batteries are used in various transport devices, although Toshiba has produced something that's suitable for larger consumer devices, for things like power tools and Roombas.
Lithium
2. Haptics tech using the coulomb effect designed by senseg. You can find info at senseg.com. Basically it's haptics that can give smooth surfaces a texture. Imagine if you will, touching the iPhone glass and having it feel like fur, or sand, or even skin. It can give the sensation of a real physical keyboard, including delineations for each key. This is obviously a lot more sophisticated than a simple "buzz" every time you touch the screen. The best part? This tech is available NOW and can be made available in the next iteration of the iPhone.
3. Wireless keys. I have BMW comfort access, and I love it, no need to fish for your keys in your pocket, touch the door and it unlocks, press the start button and it starts. Something like Comfort Access but available for all types of locks. No more carrying key rings or looking for your keys and taking 30 minutes to find them. I'm not talking about NFC, this tech doesn't require you to put the phone next to the door, just be close enough and touch it. Again, this tech is available now, just waiting to be utilized. Sure, you'll have to upgrade your door locks and stuff, but it makes things sufficiently easier that I can easily imagine demand for this feature.
4. X-ray vision on the iPhone. Admittedly, this feature is probably not quite ready to be implemented like the other two, but I'll throw it in for kicks. A couple of guys at the University of Texas have invented a way to implement a terahertz range electromagnetic imaging device on a chip. Terahertz range imaging devices are commonly found in airport scanners that see through your clothes. Read about it at Masable:
Cellphone that sees through walls closer to reality - FutureTech on NBCNews.com
5. A companion device that can be worn on the body that can act as a both a local receiver and a sensor. I imagine something similar to the previous generation iPod Nano that can be worn as a watch or something similar. This companion device would act as both a notification device connected to notification center and include an array of additional sensors. The sensors could be used for an array of different functions. One simple function would be to act as something like a pedometer. Additional sensors could be more sophisticated including multiple chemical sensors that can act as both safety alarms, such as detecting carbon monoxide in the environment or alcohol in your breath, or as health monitors for things like blood glucose levels by checking acetone levels in your breath. Admittedly, this one is a LONG shot, but the tech already exists so it's a question of implementation.
Anyway, that's my wish list for the iPhone 5s. None of this stuff exists yet on a cellphone or exists only in a rudimentary form (haptics). I wanted to get past the basic stuff like faster processor and such which are givens. I also didn't want to stray from the design of the iPhone 5 since more than likely the next iteration of the iPhone will have the same body, so I didn't include things like 4.5" screen or anything that would alter the physical shape of the phone. The techs I've listed are either available now, or at the very least, in the very near future.