According to Jason Schreier's reply to his own article on Kotaku:
We heard from a tipster about a month ago that the Wii U version had been "postponed indefinitely." We reached out to Sega, and they denied it. I'll let you guys fill in the blanks there. :)
Also Amazon no longer lists a Wii U version of the game.
To clarify again, there's no confirmation of this. We heard it from a tipster, Sega denied it, and today Sega told me they're not commenting on anything.