In a recent interview, the creators of Mass Effect revealed that DLC, used with Mass Effect 2, will bridge the gap to Mass Effect 3.
It’s hard to say. 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.
Bioware then said that they will not be ready to talk about Mass Effect 3 for a few months.
Source: Videogamer.com