Win32 will continue to have critical parts of the API break or be depreciated. UWP will continue to gain exclusive features. Don't be surprised when DX13 has UWP only feature or is eventually UWP only. The future of windows is a closed platform. Microsoft is going to take their cut of all software purchase on their platform or no one is. The app store is coming and it's taking no prisoners. Windows 10 wasnt free, it was payed for with the freedom of the platform.
Well, Trigger rumble is one such UWP exclusive feature already. (It's part of XInput, which is part of DirectX).
Imo, expecting 100% closed system is bit too much.
For GPU access, we do have Vulkan, which makes it harder for MS to close DX, as it's likely that all rendering features will be both DX and Vulkan. Vulkan on otherhand should make it easier to do Linux ports.