Wii U confirmed to be able to transfer downloadable content from Wii to Wii U, similar to the way DSi users could transfer their purchases to 3DS.
Nintendo is also looking at overhauling how their online purchases are carried out; probably through having each Wii U tied to an account with several sub-accounts for different users.
Games and peripherals designed for the Wii have already been confirmed to be backwards compatible with the Wii U.
No official word on whether the console will be able to patch Wii U games (possibly) or Wii games (unlikely).
And of course, this still isn't going to help RB1, Lego, or AC/DC export.
Those of you who haven't yet made the switch to 360 or PS3 because you're in too deep now have a little light at the end of the tunnel; Wii Rock Band isn't dead just yet.