hopefully modders will be able to take advantage of the Dx11 features
Don't expect that to happen for several years, IF that happens at all. Modders have to hack DX features in. With a new engine, that even lowers the chances, as it will be so much new for modders to learn and understand differently than before.
Most likely, modders will never be able to take advantage of DX11 features. It's really hard, takes huge amount of time and dedication. Very very few people know how as well.
The modders have even spoken themselves in a few threads here. This something Bethesda has to do from the start. Don't expect modders to do it for Skyrim.
Most likely, if we don't get any DX11 features from the start, we never will.