I really don't believe this at all.
It is going to help the Xbox 360, but there will probably be more titles for the PS3 motion tech already, and there will certaintly be more Wii motion tech titles available.
They should be positioning the 360 Natal pairing as cheap, uber-easy to use HD motion tech gaming. But its not going to be the equivalent of a new launch.
The only issue with that is Natal is rumored to be very expensive.