I don't expect much DLC for this, other than making the pre-order/deluxe content available. I would be very surprised if they tied any story content into DLC, I think that would infuriate people too much, particularly before the "full game" has been released.

Maybe a couple of cosmetic things, and gameplay-wise perhaps some kind of challenge mode content. Completing certain chapters/bosses against the clock with harder enemies, a boss arena, that kind of thing. I hope we don't have to worry about anything like that, but I reckon they could get away with if they were determined to squeeze some extra cash out of us before part 2.