It will sell at least one ;)
I will wait till it hits budget price, but knowing the trend of Wii U third party title prices dropping like a rock, it shouldn't take long. I think the gamepad will be a good fit for this game. Kinda done with my 360, and I'd rather get the better graphics at (probably) a lower price. My PC MAY be able to handle it but I'd rather not take the risk.
Anyway, in regards to the topic: I'd say about 350k.
"We hold these truths to be self-evident - all men and women created by the, go-you know.. you know the thing!" - Joe Biden