I think it will get an M. The darker setting and tone coupled with the fact there's a civil war will put it onto M territory.
Neither of those things would make the game an M. It's the blood and the mature themes like drugs that would do it.
As for the comments like "I won't buy it if it's not M" and such, really? This game will almost certainly be M, but 90% of what is involved in TES would fall just fine under the T rating. It's the drugs and more grizzly corpses and such that push it into M territory. Oblivion would have easily been rated T without the drugs and the more detailed gory corpses.
Pre-Morrowind sixual themes might have pushed it into M territory. In Morrowind and Oblivion the sixual themes I know of would still have been in "T" territory. People are really underestimating what passes with T.
Edit: I see this person beat me to it.
there's plenty of games that are T that have blood :S