The newest Mario kart for the Wii U, is the best of the series by along shot.
Its basically the only "must have" game the Wii U has atm (imo you cant own a wii u and not have it).
So how will its sales be on a system where most already own a great racer? and its has mario in it....
I dont think the game would have sold that well on the Wii U anyways, so probably no big loss for the developers.