AvP has it.
DiRT 2 has it
Battlefield has it.
Metro 2033 has it.
...and I only mention the ones I'm absolutely sure they have it.
Unique Heaven has it too.
Tom Clancy's H.A.W.X 2.
S.T.A.L.K.E.R.: Call of Pripyat.
Civilization V partly uses it.
Lost Planet 2.
All in all, that's very few games in total. But it shows hope that if a game has DX 11, it often use tessellation for all the game, or some parts in the game. So it's hopeful.
The way things are, I don't think DX11 will be included... I just have a feeling that it isn't an area Bethesda is going to cover. DX10 support seems more likely. Maybe they could support DX10.1 as that supports tessellation, but I think full tessellation on such a big world might bog down all but the top end systems. Maybe this is why they might not go with DX11.
DX11 could always be added later though, even after release. DX compatability isn't something that needs to be coded into the engine from the ground up, it can be patched in.
The performance drop from DX10 tessellation is huge compared to DX11. I remember some NVIDIA guy saying somewhere that DX11 can use tessellation at a tenth of the performance otherwise, or something like that.
Also, tessellation doesn't have to apply for all objects. From the benchmark tests I've seen, a game that otherwise runs on ... say 120 FPS, will run on about 90 FPS with full tessellation on. At least that's what the benchmark tests I've looked at has shown.
And yes, you're right, DX 11 can be added later on. But why on earth would Bethesda add DX 10, just to later patch in DX 11? That would be really dumb
In all hopefullness (if that's a word
), maybe awesome Timeslip could add DX 11 support from DX 10 ^^
Looking at what he did for Morrowind, he should be working at Bethesda