Disclaimer: I don't own or play video games, and never will.
I think Kinect (or at least the technology behind it) will be very popular, but not necessarily for gaming. The lag is too great, the resolution not high enough. What it could do very well, is be a virtual teaching tool. Some examples:
virtual yoga (it recognises speed, posture, balance)
virtual martial arts teacher (especially when learning kata)
rehabilitation (relearning stroke victims to walk, etc.)