The Wii U is very capable of fully emulating a GameCube. Various people have shown it to be able to load a GameCube .dol/.iso from an SD card in the hacked Wii interface and play it without any slow downs. Because of the PowerPC chip that drives the GameCube, Wii, and Wii U, the emulation would be fairly easy to accomplish. The worst part is that GameCube games are not overly pretty in 1080p. Nintendo could possibly use some of the extra CPU/GPU power to upscale the content, but sadly it would all have to be downloaded as the Wii U's optical drive cannot work with the GameCube mini discs.