Tremendous find by MTBS power-user DmitryKo! Looks like Microsoft has officially acknowledged stereoscopic 3D support in the upcoming Windows 8 DirectX 11.1 release. It's just a preview document, and there are more unknowns than you can shake a stick at, but it could mark a major breakthrough for native stereoscopic 3D support in PC gaming.
Awhile back, MTBS met with Microsoft to talk about DirectX potential with stereoscopic 3D, and their interest goes well beyond gaming. It's actually the simple things that DirectX can effectively solve: like windowed 3D support, 3D video chat systems, and more. While this is a supposition on our part, native stereoscopic 3D in DirectX would quickly erase forced brand preference, and help increase compatibility with multi-GPU systems.
Native or not, DirectX still leaves artistic choices in the hands of game developers, which doesn't always guarantee the best 3D experiences. It's also possible that 3D support in this path is limited to the DX11.1 spec and won't work with games targetted to DX9 and DX10 systems (even natively written). We'll have to see how things progress!