I do not think that Natal is a simply reaction to the Wii.
Check this video: Bill Gates talks about Natal more than two years ago. (it was so obvious but we did not see it!)
http://www.youtube.com/watch?v=D_rxpAgBFQo&eurl=http%3A%2F%2Fwww%2Eyoutube%2Ecom%2Fuser%2FKenzoki&feature=player_profilepage#t=410
He talks about the Wii and how Natal is different. They probably worked on this before the Wii was released.
Check 6:30.
The whole interview with Steve Jobs and Bill Gates is great. I can highly recommend it.
Imagine not having GamePass on your console...







