This game won't be a system seller alone, I don't think. But added in with the games already out and the games upcoming, it's one more "plus" for the console and could drive sales eventually. Considering that it's one of the bigger Wii U games coming out in the next few months, Nintendo should try to effectively market it, if not to sell the game then to at least raise awareness of it and the Wii U as a platform with attractive exclusive games.
People putting focus into a game like this is a good thing. Like I've said about Rayman Legends in the past, on Wii U that kind of game gets a lot of attention that it may not get elsewhere. A game that normally doesn't seem like the most interesting development on any other console is put into the spotlight on Wii U. This is NOT a bad thing; it means that deserving games get the right amount of attention and press rather than being "thrown into the pile."
Also, thinking about the Wii U's current and upcoming library, you can say the Wii U has NSMB, Nintendo Land, Pikmin 3, Lego City Undercover, Bayonetta 2, and Wonderful 101. I'm just using these as examples. Anyway, that's a diverse selection of high profile EXCLUSIVE games, which definitely helps the Wii U sound like an interesting alternative console. What I'm hoping for the Wii U is that it eventually sells based on pure differentiation and not just "being an X360/PS3 with Nintendo games."