Rockstar updated its graphics engine (RAGE), so it would not be compatible with the new Nintendo console (Wii U) or the Sony PS Vita, which required an x64 microprocessor to be executed, something that the Wii U does not have, it only has one Espresso x86 microprocessor, the same happened for Unreal Engine 4 that used an x64 microprocessor.
GTA V for Wii U seriously, I always thought Wii was for kids and grown men jumping around like kids. I've seen the Wii U on youtube and i doutbt Rockstar would put such a hardcore game on such a kiddy console, and if GTAV gets delayed because "complications with the WII U version" Whats your t NgUz44.