Wii U "fans" aren't buying Wonderful 101, Wii Fit, Pikmin 3, or DKC. I don't think you have anything to worry about with Watchdogs or any third party.
It was never going to sell well on the Wii U.
This is a system that's going to sell some copies of Mario Kart, Smash, and maybe some NFC toys for Nintendo if they're lucky and not a helluva lot else. It's a niche Mario box.