AFAIK, possibilities for the use of DX11 will be there for PC, so it will be there for Modders.
But it won t be taken in account for Skyrim, all platform will equally display slow and limited DX9.
IF TES VI is UP, and console accept DX 11 at this time you will see it in TES VI, if not, forget it.
I just want to make something very clear here about DX 11 and modders taking use of it:
I've spoken to one of the creators/contributors of OBGE (Oblivion Graphics Extender). He said that it will take years for a Skyrim Graphics Extender to come out. To implement DX features in a closed-source engine is VERY hard. You can't implement it normally. First, only very very very few people know how. Second, only even fewer people actually have the time and urge to spend so much time doing this. Third, modders are forced to "hack" DX features in. It's a whole lot harder for modders than for developers to implement DX features.
Do not expect a Skyrim Graphics Extender to come for a long long long time. Say, several years. Or don't expect a Skyrim Graphics Extender to come at all. Timeslip is the modder who is responsible for creating the foundations of both OBGE and MGE. I'm not sure what he/she is doing right now, but if it's someone who's good at creating these utilities, it's him/her. Shademe could also help, as he's been developing a lot of the OBGE.
Don't ever expect modders to add tessellation btw. Something like that would require immense amounts of works for a modder. It's not as easy as pressing on/off on a button.
In short: Don't expect modders to take use of DX 11 features. Most likely will never ever happen. And if it does happen, expect it to take many years.