While its completely possible, R* is not friendly with Nintendo. They tried a GTA game (albeit a crappy one) on the massively popular DS and it didn't do great.
Personally, I think it would be stupid not to. However, its initial development went to PS360 and if anything Wii U would get a straight port like COD or AC3 where they didn't have time to improve on anything due to the hardware beyond some uniqueness given the Gamepad.