Will Natal and Move pressure Wii to give higher quality content?

[Voltaire]

If you mean 1st party content (and i think you do), then probably not. Nintendo is already doing a hell of a job in that department.

If you mean 3rd party content, then no again. If a AAA 3rd party game hasnt been released on Wii after 3.5 years, chances are it wont happen now.