I'm hoping that we get to see more of the political character which made the first game's universe such a gem to me. ME2 gave us plenty of culture, but it shoehorned the politics that made everything about Shepard work, in my opinion.
But my best assessment on the series would be to divide it into three motions: Mass Effect was about the threat and introduction, and Mass Effect 2 (should have been) about the arrival. Thus, the third can be about the total war between the organic species and the Reapers. Everything's been cleared up, Bioware - you don't need to dally time to build any more tension. Just start with the war.