I'm assuming that the endgame save or final save or whatever you want to call it for Mass Effect 2 is created after your decision regarding the Collector Base.
What I wish to know, is: will it re-save with new information based on any DLC I complete?
For example, if I finish the main mission, and then proceed to finish the Arrival DLC, will my final save be updated so that in ME3 it knows I finished the Arrival DLC?
The reason I ask is because I know there could be some effect in ME3 based on what you did in DLC, so if my final save (I'm almost there) doesn't update, then that means that I'll want to complete all of the DLC before taking the fight to the collectors.