Next-generation iPhones likely to focus on internal improvements.
Apple Patent: Visual Buttons?
Essentially, Apple describes the use of buttons which provide visual display on the button itself to provide dynamic information. While it could be used in any electronic device such as laptops, PDAs, cell phones, the application describes the possibility of its use in a "standalone device" such as a remote control.
The goal of this technology would be to streamline the user interface for users.
"By reducing or eliminating the input devices, the display of the electronic device can be maximized within the user interface portion of the electronic device, or alternatively the electronic device can be minimized to the size of the display."
There have been previous unconfirmed rumors that Apple was working on incorporating "color LCD buttons" alongside the trackpad on Macbooks. A similar concept is used on the much publicized Optimus OLED keyboard.