I doubt there will be much physically changing. Aside from the vocal minority that wants a front-facing camera, there isn't much worth adding. Maybe an infrared sensor on the top for some remote control application (rock on), but that sounds like old tech for Apple. I wouldn't complain with another button or two on the right for camera features or that could be customized like my very old Razr.
The one physical thing I could REALLY go for is interchangable plates or covers. The big, thick cases are nice, but it would be better to customize the phone without needing to add bulk. It would also be nice if you have any accessories that aren't case-friendly, like the mount I had in my car. Sorry, but I'm not taking the darn case off EVERY TIME I get in my car and then putting it back on EVERY TIME I get out.
Internally, probably just minor bumps. Next year's will probably be the big 4G upgrade, so I doubt there will be more than maybe spec bumps.