Coming from IGN:

Besides confirming a global release in 2010 on Xbox 360, PlayStation 3, and Nintendo Wii, the the track list will be fully exportable, allowing you to play the songs or Rock Band 1 or 2. This exportable option is only for PS3 and Xbox 360, not Wii, however.

That is a big blow for the Wii, but darn you Rock Band, you are going to have to make me buy my first ever Rock Band game!

Link