Exactly right. At maximum graphics, on PC it will look exactly like the console versions. And if it keeps the same level of quality that we saw in the trailer, probably better by November, then it's gonna look awesome no matter what you play it on. Don't forget as well, that the trailer was filmed on a 360. And like you said, if DX11 is supported, then there's nothing stopping the PC modders from ramping it up anyway. I think, keeping it on a level playing field is a smart move. It makes their job easier, and it gives an even starting point from a player point of view, with modding etc. I don't think there's anything to worry about. Just sit back and enjoy it when it comes out. It's already significantly better than OB, and that's what matters right now.
Just want to clarify:
Modders won't be able to add DX11 features for a long long time. And perhaps then, they might not even be able to. The modder responsible for both graphics extenders (MW and OB) is Timeslip. He started the projects and made both foundations. He should be able to add some DX11 features, but most likely not tessellation (as I understand, that requires you to alter all the meshes/textures in the game). Perhaps shademe can help too.
Still, as I said before, it takes A LOT of time for modders to add DX features, or even shaders. And first they need to "hack" it in. They can't implement it normally as developers can. And when they "hack" it in, other problems occur, etc etc.
Expect a graphics extender for Skyrim to take years, or if we're unlucky, never come. There are very few modders that know how to do this. Very very few. And not all of the few that do know how have time, or the urge do put so much work on something like that.
So, basically, DX11 without any features would only give us better performance, even though it COULD give us so much more from the start.