I believe Microsoft have said that the next DX update will be an Xbox One and Win 8.1 exclusive. This is obviously not for technical reasons, but to force people into their particular walled garden.
However, they'll possibly change their mind later when the howls of outrage begin.
Tbf alot of games don't even use all the features of dx10 never mind dx11! Also from what I've seen the dx11.1 on w8 doesn't really add that much extra that dx11 on w7 etc already offers. I've not seen anything that says dx12 is to be released any time soon.