In a recent interview with CVG, BioWare producer Adrien Cho assured that the plan isn't to jettison Mass Effect 2 into the deep, dark retail space without some form of continued support. According to Cho, some of the core development team has already moved on to creating DLC for the game, which could range from new items, including weapons and armor, to side quests that might even build "up to full expansion packs." Cho added that the team has more flexibility to create DLC for the sequel than it did for the first game, explaining that add-on content "was always on our radar from day one."
It sounds like BioWare has big plans for Mass Effect 2 DLC. That is, it sounds like the plans are a bit more sophisticated than the original Mass Effect's DLC strategy: "release completely broken, partially inaccessible DLC without telling anybody about its existence."