A photograph that probably depicts the Nexus Prime, makes clear that Android 4.0 Ice Cream Sandwich makes it possible to produce devices without hardware buttons.
With the tablet version of Android, Honeycomb, it was already possible to a make tablet without physical buttons. Instead of the buttons can be found in a kind of toolbar that is displayed at the bottom. The pictures show that the smartphone version of Android is about to use a similar concept. Manufacturers thus can make phones of which the front (almost) entirely exists of screen.
Sharp has previously showed a phone with Android Ice Cream Sandwich. This handset does have physical buttons. It seems that a button-free device is an option, but not an obligation. It is expected that the new version of Android is shown to the world on Oct. 11, when probably the Nexus Prime is revealed as well.
Source: Gsmarena.com