In all honesty, I can't see it doing that well. Existing Wii-U owners may well buy it, since Japan's release schedule is absolutely barren at the moment. But I can't see it pulling in many new people to buy the console, because it's a lot of money to drop to play a slightly upgraded version of something (to draw a parallel with the west: people didn't buy a Wii-U to play the best versions of Arkham City & Mass Effect 3).
I'm not sure the game is all that popular anyway. It's made an extremely respectable amount of physical sales on Wii, but the true testiment will be how many people are still playing & subscribing every month. BaldrSkies said that a lot of people just play during... kids hour or something? There's a free-to-play hour every day or something like that.
But who knows. Perhaps people didn't buy the Wii version because they knew the Wii-U version was coming. It is Dragon Quest after all, one of the 4 biggest IP's in Japan. So it's a bit of a wildcard, I'd say.