@superchunk
Most development companies just use a separate team for the Wii. There's no way porting a Wii version to an HD console will ever fly.
EDIT: I should elaborate. There isn't a magic "Make this game HD" filter. If they mae the Wii version first, they would pretty much be making the entire game over again in order to port to the 360 or PS3.
My End of 2008 Hardware Predictions (console only):
Wii : 50 million
360: 28 million
PS3: 24 million
These predictions were made on January 3rd and won't be revised