I know that the 360 never will be a second Wii even with Natal.
Nintendo has the family friendly image since ever. To create an image costs time money and its difficult.
Btw Natal doesnt look to me very promising at the moment.
Xbox 360 has to get more exclusives and a slim that would make it selling more.
Xbox needs more Alan Wake and Gears of War, Halo reach together with a slim more reliabilty and lower price. That would make it sell more.