Mostly likely BF3 will be fundamentally the same game on both console and PC just like BC2. The PC version will simply remove DX9/ XP support for marketing reasons. Firstly it makes you upgrade to Win 7 + DX11 hardware. Secondly they will able to boldly claim the game was "built from ground up" for Dx11. This way Nvidia, AMD, Microsoft as well as DX11 hardware enthusiast will be happy. But it will be really naive to think they really code the PC version independently from the console version.
Besides, if they aren't using tessellation, there is not a whole lot more that can be done on DX11 vs DX10 or even DX9. Ambient occlusion and AA are artificially locked out in BC2 DX9. But there are a ton of (better looking) DX9 games out there running ambient occlusion. Crysis 2 and witcher 2 just to name a few. And AA in BC2 DX9 can already be enabled with recent catalyst drivers. The whole talk about how DX11
IF PROPERLY IMPLEMENTED will be better performing, better looking, night and day...blah blah better than DX9 remains pure speculation to this day. 2 years on since the 5800 series we never saw that happening.
BF3 Alpha DX11:
http://www.youtube.com/watch?v=y3pVMic875Q&feature=related
BCBF2 DX9:
http://www.youtube.com/watch?v=nNdHo6ZvJEw
For a game built "ground up" for DX11 exclusively it sure doesn't look any better than BC2 in DX9!
Edit: I run Win7 + DX11 capable video card so i am not saying that just because I can't run the game.