First and foremost, like just about everyone else, I would like to see an OLED screen on the next iPhone. it is thinner, more power efficient and more vibrant than LCD. In addition I thinks it is about time for a resolution boost.
Second, battery life. Rather than make the phone even thinner for no reason, keep it at the same thickness (or maybe even make it thicker) and give me much better battery life
Third, Wireless charging and quick charging. If I have to charge my phone during the day I want to get a quick top off that will last me until I get home
Fourth, smaller top and bottom bezels. This way we could get a larger screen in a smaller form factor. I'm mean the size of the plus phones is just ridiculous for the screen that comes with it.
Fifth, NO MORE CAMERA BUMP!!!! if the cameras are so big that they need to stick out then add more battery to the phone and make it a bit thicker.