From the point of view of pure game design and planning, what are the technologies of the next-gen (post-360, PS3, and wii) consoles that I can anticipate for my design? In designing a new game, I want to leave it open-ended enough to incorporate the new technologies and start planning for future gameplay. Depending on the technologies, I might also want to change the style of gameplay.
A lot of your question depends on the type of game you are making. Recently, the big 3 game consoles have put a lot of effort into motion control based systems, and personally I expect that trend to continue.
However, there are 2 distinctly different approaches at this time. The Wii / PS3 approach involves handheld controllers combined with motion. The 360's Kinect eliminates the controller entirely and relies on pure player movement. Both have been relatively successful, so it is hard to anticipate which approach will be more adopted in the future.