Splatoon is scheduled to release this year on the Wii U as a brand new IP with the ability to use amiibos and in terms of controllers for Player 1 it's strictly GamePad-only while Player 2 can still play with the Wii U Pro Controller.
The UK retailer The Game Collection has the game on pre-order for £27.95 which in Dollars converts to $41.40 so it's very likely that this is yet another budget game. Makes sense because it'll sell better that way than charging £32/$60.
Regardless, I won't be pre-ordering it even for a low price. No Wii U Pro Controller support for Player 1 no buy.
Edit: Another UK retailer this time GameSeek has Splatoon on pre-order for £25.00 so that even below the $40 price point completely ($36).