A couple details from my issue of GameInformer:
-The first few levels detail Hawke's escape from Lothering. This happens during the events of the first game, so you'll get to see some of what happened from a different perspective.
-Flemeth and Morrigan will return
-The narrative (at least in the demo and opening levels) is in structured as a story being told after the events of the game. A seeker from the Chantry, wanting to stop a war, meets with a dwarf named Varric to ask how Hawke escaped Lothering. Varric tells her story, but is only telling her what she wants to hear a la Keyser Soze, while the real story is seen from your perspective .
-The reason for the decade apart between games is to make the story about Thedas rather then a specific character. (They mentioned Mass Effect as a counter-example, how the whole thing revolves around Commander Shepard.)
-More specialiizations for classes
-They're not doing that thing where companions gain or lose approval for every little detail.
-The Darkspawn are still around, though they're not as big a threat as before.
-The driving force behind the story is how Hawke came to escape Lothering, travel to the Free Marches, and become the Champion of Kirkwall.