Wouldn't it be cool to add this to the game? It would make the graphics look even more amazing. They could make it like WoW where you choose which direct x to use for people that dont have dx11. Its definitely something id love to see in the future updates.
The version of directx used really doesn't have much to do with how the game looks. A few extra x effects possibilities, maybe a bit better performance on some renders. That's it really.
Like Lurkios said it really only adds capabilities. A 1200x1200 resolution picture is still going to look like a 1200x1200 res picture after adding dx11. All it does is raise the possibilities that the programmers can use, but it doesn't do the programming and artistry for you.