"We have a bunch of packs that are in the works right now. So, for the time being there's going to be a continued stream of DLC for people. We'll start to have packs that'll tell the story between Mass Effect 2 and 3. But beyond that we kind of have to see how people are responding to what we have and go from there."This would an unexplored use of DLC and probably a more compelling reason for gamers to get the DLC packs, though none of the DLCs released to date are part of this idea. This leaves the door open for a great deal of DLC packs programmed for Mass Effect 2.
Hudson commented that no features of the game will be revealed in the coming months, so probably an E3 reveal is not probable... new DLC on the other hand, could be a possibility. If they handle this well (We can trust BioWare on that) it could be that players would be really up for a DLC content that would be part of the main trilogy's story, it all depends on how many are planned to tell this in between story.
BioWare's guys are smart... Mass Effect 3 is scheduled for Q1 2011.