Microsoft: All our games will use Kinect

"It's not a mandate that everything we do in firstparty has to support Kinect right now," said Phil Spencer of Microsoft Games Studios. "But I will say, specifically with voice, that there are some things that just seem to make navigating and playing games so much easier, that I would guess the answer will be yes in the end, that you'll see all firstparty games using some form of Kinect functionality."

Source: GameSpot