Do you have a source of this "promise" of DX11?
I do not recall them promising DX11 before Skyrim came out.
Here:
http://www.tomshardware.com/news/The-Elder-Scrolls-Skyrim-Todd-Howard-RPG-DirectX-11,12495.html
And Here:
http://www.pcgamer.com/2011/04/19/the-elder-scrolls-v-skyrim-mostly-a-directx-9-game-directx-11-support-a-possibility/
It would be nice to have DX11 to boost performance, i think the game looks quite good as it is, but its always good to have extra fps... but to be honest, i doubt they ever do it... Todd is known as Maiq also.