In Mass Effect 3, the fans have asked for content that clarifies the ending and meets what the developers said in pre-release comments. The press is reporting that Bioware is looking at ways to extend the ending in the form of DLC or a patch. To do this, the ending of Mass Effect 3 will have to change. Many in the industry are opposed to this change.
The analogy is similar in that the ending in both games will have additional content after release, and that this content will address issues that were present in the original ending. [Fallout 3 - Fawkes]