Of course this game won't use DX11. They're using nearly a 5yr old graphics platform. This game doesn't look much better than Fallout 3 which is sad as Fallout 3 wasn't a good looking game at all.
Bethesda has been using the Gamebryo engine since Morrowind (obviously newer revisions since then). It's a 3rd party engine, so it has been undergoing development in the interim by the vendor. They added PhysX support 18 months ago or so, for example.
http://www.emergent.net/en/Clients--Titles/