One of the main new features in DirectX 11.1 is support for 3D monitors, meaning you will no longer need extra software to play stereoscopic 3D games.
Microsoft employee Daniel Moth reports on the Microsoft Answers Forum that will remain exclusive to Windows 8, and that the latest version will not be released on Windows 7. Although it's unlikely that there will be DirectX 11.1 only games in the near future, it does mean that an upgrade to Windows 8 is required to play them.