A Nintendo exec mentioned an interesting tidbit about the Wii U and GameCube game compatibility during an interview with Nintendo Gal at E3 2011. Amber McCollom, Director of Entertainment and Trend Marketing at Nintendo, said that a number of the games that were playable on the GameCube can be downloaded from WiiWare.
When discussing backwards compatibility, it came up that Nintendo usually goes back one system when a new system is released. So the Wii games and accessories were compatible with the GameCube, and the new Wii U will be compatible with the games and accessories of the Wii. The good news is Nintendo seems to be throwing GameCube owners a bone, making some GameCube games downloadable on the new system software/hardware as well.
Some people have doubts about whether this WiiWare downloadable content is going to materialize, and not end up another Nintendo urban legend. Personally though, I don’t see why Nintendo wouldn’t offer this incentive to encourage sales of their new product, and to entice gamers to make the switch if they’re GameCube owners.