You have the choice of platform, they'll send the survey out at the end.
Alpha expected around Dec 2014 to Feb 2015.
They've added more clarification to the Wii U port in the FAQ:
Also the Wii U is by far less powerful than XB1 and PS4 and have less memory, also our engine is not in the same version on PC/PS4/XB1. The Wii U version is an older version, we are already working on Wii U but for all that reasons and the asymetric gameplay we want to create, the Wii U version IS another version it require us to "recreate" the game especially for Wii U when other platforms is basically a one button export, and that justify the very reason of the goal, it's a real challenge and it deserve to be a higher goal.
I now want "one button export" to be a meme