BTW if Microsoft chooses to go opensource one day they can just start improving Wine together with CodeWeavers, ReactOS team and the community to the point when it could replace Windows completely. This is approximately the way they have chosen to go with their web browser switching to the Chromium Blink engine.
I bet Microsoft has an absolutely killer win32 regression suite. If we're devolving into pipe dreams, I'd probably want that even more than the actual win32 code.
I'm sure it wouldn't be impossible to kitbash this release with WINE and get it working on Linux.