Quantum Break has appeared to be showing up on the Windows 10 store, can't buy it yet.

UPDATE: Quantum Break’s download size will be 36 GB on Windows 10 and 44 GB on Xbox One.
Quantum Break is a time bending third-person shooter from Remedy Entertainment. The game has been quite the story over the past few months with the surprise of it coming to Windows 10 along side the Xbox One. Now it appears that Quantum Break is showing up on the Windows 10 store ahead of its April 5th release.

Thanks to Windows Central for pointing this out.
Those who purchase Quantum Break on Xbox One will also receive the Xbox 360 version of Alan Wake and all of its DLC for Xbox One’s backward compatibility. Not only that, if you pre-order Quantum Break on Xbox One you will get a Windows 10 key as well.
Quantum Break is around the corner and you will not want to miss more coverage on this game.