Yachtclub, the makers behind the game, already submitted the game to be verified by the platform holders. It means that the game is pretty close to be available.
Meanwhile, they are still accepting Controller submissions, so they can be supported on Steam. That's right, you can submit your old (or new) controller, so it can work when you get a Shovel Knight copy from Steam.
Here is how:
Supporting controllers on Steam is hard! If you have a controller that doesn’t work with Steam, you can go here to help us: Controller Binding PageEach controller that you enter, we can make work with Shovel Knight on Steam and PC!
easy!
You can also check which controllers they have so far HERE (..and as you can see there's also room for Mac and Linux)
Hoping someone at least submits the Wii U Pro controller (with the MayFlash adapter)
And here, the latest trailer for those that don't know much about the game: