DX11 is way ahead of OpenGL, even John Carmack said so in a recent interview. Then again, Carmack also said that his upcoming games are all being made in OpenGL so take that for what it's worth. And even though DX11 > OGL, the PS3 uses OGL.

The main differences between DX and OGL is that OGL tries to support old hardware for as long as it can, while DX with every new generation basically sets a minimum and if you're below it then TFB. It won't be long before OGL catches up to DX11, but it's really up to S-E whether they want to continue supporting old hardware and multi-platform or if they want to set a hard minimum for what hardware can play their games.

Now, all that said...
  1. Modern games still use DX9. See The Witcher 2, which was just released as a DX9 game. Witcher 2 is a high graphics game.
  2. Jumping to DX10/11 won't make the game better.
  3. Enabling DX10/11 may allow modern hardware to run the game more efficiently.
  4. Patching in DX10/11 support is relatively easy compared to rewriting the entire engine because your knickers are in a twist.
  5. S-E is managed terribly so don't expect any miracles.