So far, leaked images like those in the gallery above point to minor, cosmetic changes, rather than a massive overhaul.
The application drawer could move away from the all-black background in favor of a transparent bar. The pervasive notification area also appears to get the same treatment; a few screenshots show the top bar as having the see-through effect. In a related note, a 9to5Google report shows the notification bar with colors that match or complement various apps. The dialer app, for instance, brings up a blue bar, while the Hangouts app has a green one. It’s possible that these particular apps were designed with their own colors and that the transparency is otherwise still present.
According to Italian Android blog TuttoAndroid, the lock screen will include shortcut to the camera application. The move would make sense as most custom launchers and lock screens have moved to integrate the oft-used feature.