I think they should remove the L2 and R2 and add a multitouch pad on the back. This could work as an alternative to L2/R2, or used for 1:1 instant aiming, grabbing/moving items in the game, selecting stuff, etc. the rest of the buttons should stay they same.
They could add a mic and camera in every controller for video chat without accessories. If they wanted to get really advanced, they could have the back touch pad simulate the texture of in-game surfaces (adding a new sensory dynamic).
Adding stuff like front touch surfaces would interfere with game play as you would have to let go of the face buttons and/or analog sticks. Motion controls haven't been well mixed with traditional controls by game developers, though IR aiming has done well. Full body motion hasn't been mixed with regular controllers because it glues your hands together. And controlling a game with your mind is still not feasible.
Not sure what else they could try, but i hope they don't try mixing controls they interfere with one another (it can really make game play awkward).
