Xbox 360's Will killer? I'm confused, why are we trying to kill Will Wright again?
But seriously, Natal is not going to be the "Wii-killer" that some people think it will. More likely than not, you're going to see the same thing that happened to the Wii in the beginning happen to Natal: A few good games that take advantage of the technology, but a lot more shovelware games made for a quick buck. In fact, we're also probably gonna see this happen to Sony's Wand. This kind of thing happens with any new technology in games, and it's a sad thing to see no matter which system you own.
On-topic, I'd really like to see if Milo can actually live up to the hype that Peter Molyneux loves to exaggerate so much.