Just a quick reminder:

DX11 features are really about making the game look better and most important, to better use GPU and scale up with GPU power.

Then there is stuff like ambient occlusion that is so poorly implemented and unoptimized that you can't really blame it on DX9.

So really, DX10 or DX11 won't bring any significant boost on current hardware. What they need to do is optimize the engine, once they've got that they can start thinking on using DX11 for eye-candy and future proofing.