Well if GTA V does release on the Wii U, I'm sure it will look horrible.
That screenshot is almost certainly edited. And the Wii U has like 1.5 times the power of the 360 and the PS3.
Texture popping. Common issue even on this gen. Just a skillfully taken screenshot. The Wii U has 2 gigs of dedicated video ram, and 16 gigs of regular ram. Plus, arkham was just a port. Wait until games start being built from the ground up just for the Wii U. New Super Mario Bros. U looks really, really sharp.