I'm thinking that it will provide a small to moderate sized boost. Wii U sales will go up a double digit percentage in Japan, but will fall back down to the usual within a couple of weeks. Still, the game can likely have legs, and I fully expect it to sell at least a quarter million lifetime in Japan on the Wii U.
That honestly seems like a lot to me -_-
Is the game playable only on the gamepad? I it is, and they market it as such, I think the sales could get a lot better.