I reckon the 720 will have Kinect built in with the ability to turn off, better graphics (lol), most of the features of normal Xbox, harder to hack, maybe a built in capture card (will make the price soar) ability to play all 360 games?, the pad designed different maybe like a combination of PS3 and 360, all games will have a 3D option... and that's all i can think of atm :L
Also, first post!