This is difficult to know at this point, as we have absolutely no idea how the Nintendo eShop works with transactions and copies! But we will definitely try to provide backers with as many options as possible if the game gets on the Nintendo eShop!
We hear U! (see what we did there?) Like everybody else, we think that a Wii U version could be awsome! However, as stated, we are not in a position where we can promise anything yet, but we hope that Nintendo is listening to all of the great feedback you are giving!
Yes, the game supports XInput controllers, meaning that you will be able to play with e.g. an Xbox 360 controller or Logitech F710. It is also possible to play with a PS3 controller; however, you might need to use some software in order for it to work (we suggest MotioninJoy).
Unfortunately our game engine, Unreal Development Kit (UDK), doesn't support Linux natively! Ack! What a bother! We're definitely trying to work around this issue, we'll let you know if we're ever certain we can release on Linux!
Right now we're focusing all our energy on getting on Steam and the Wii U eShop! Once those have been achieved, we'll be able to spend time seeking out more options, like GOG.com, Green Man Gaming, etc.!
We really hope so! Even if you never tried games such as Banjo-Kazooie or Super Mario 64 (you totally should!), we think you will enjoy A Hat in Time. Our focus is on creating beautiful three-dimensional worlds, where you can freely move around and have fun. Many games these days are very strict and linear; we intentionally try to avoid this, because we believe a game is more fun when you aren't forced in a specific direction. YOU choose where you want to go!
Some of the objects that you will be able to collect in the game are: time objects, energy bits, pins, monster drops, hats, masks, etc.
Right now we are focusing on the PC/Mac version. Even though it would be awesome to release on all those new and shiny platforms, we are just a small team. Therefore, we simply cannot promise anything in this regards. That being said, we of course want the game to be available on as many platforms as possible.
Don't see the answer to your question? Ask the project creator directly.