Stop worrying about the feature level/graphics card. The only limiting factor here is the operating system.
DX11 can target directx 9.1-11 enabled graphics cards.
So for unity users that makes it 53.2% (Win7/Vista) to 44.1% (XP)...
Reasons for that: -Operating system trends here, here and here. -Your game will probably take a while to make yeah? So when it's done XP will have an even smaller market share.
Beta is fast approaching. Only one major feature left (greatly improve embedding)... Can any of you think of a major feature that you would like to see added? I'm going to make sure it runs well on mac/linux now.