DX11 patches seem to be all the rage for PC games at the moment, and Total War: Shogun 2's no exception, you'll be able to download its patch during the first week of May, which should also come with a couple of fixes and changes to the game's multiplayer experience.
The paragraph above would just be a load of wild rumours and conjectures if we didn't have anything to back it up with, so here's a quote from the community manager of the Total War forum, Craig Laycock:
We're planning to roll out some fairly substantial fixes in the coming weeks and months. The first stage of this is Patch 2 which, we're thrilled to announce, will also upgrade the engine to DirectX 11. This means those of you with DX11-capable cards will be able to access features such as hardware tessellation and enhanced shadowing. Patch 2 will also bring Anti-Aliasing support.