For those Windows 7 user who aren't going to upgrade to Windows 8 but still like to get DirectX 11.1, you are of luck. Microsoft is going to keep the latest version of DirectX as an exclusive for Windows 8, along with Windows RT and Windows Server 2012.
In a recent post on the Microsoft Answers forum, Microsoft employee Daniel Moth stated, "DirectX 11.1 is part of Windows 8, just like DirectX 11 was part of Windows 7. DirectX 11 was made available for Vista .... but at this point there is no plan for DirectX 11.1 to be made available on Windows 7."
If you don't know what new features have been added to DirectX 11.1, then go to this page. Microsoft has listed all the new features of DirectX 11.1 there.
Source: Microsoft Answers forum, Via Neowin