"Why do they all believe Arc and Natal will kill the Wii?"
Malstrom theorizes it's more to try to get investors and stockholders to stop telling developers to make games for the Wii. They were on developers over this since 2007, and developers have clearly been resistant. That might have been why niche games are largely announced to be tests. They know the games won't sell well, but it's not really to tell gamers what to do, but to make it look to the stockholders as though they are trying.
A flashy-first game is awesome when it comes out. A great-first game is awesome forever.
Plus, just for the hell of it: Kelly Brook at the 2008 BAFTAs