I expect specs of both systems to be very close. Maybe identical.
Both will be out fall/winter 2013.
xbox720 will come with Kinect.
PS4 will have a lot of cross-play with VITA.
I could see one, or maybe both, having controllers with a touchscreen on it.
MS will continue charging for online.... Sony could possibly begin charging too. I hope not though.
Lots of games will be available to d/l online (This prevents trade ins, and cuts out the middle man)
Long development times for games and bigger development budgets (not good).
Lots of "Apps" on both. Streaming TV apps especially.
I'd like to see them include some sort of recording device on the system. Both to record tv, and games while i'm playing.
Sony gonna come out the gate with lots of exclusives early on this time. Naughty Dog is already working on Uncharted 4 for PS4.