A free DLC for Mass Effect 3 will be released next Tuesday. It's called simply the Extended Cut, although everyone knows it as "that one that's supposed to fix the ending". BioWare has stated that the DLC will contain new content to expand upon and explain, but not drastically change, the game's final chapter. Rumors have been floating around as to which voice actors at which secret meeting may be involved. According to the BioWare blog, the end will clarify some plot points as well as expand upon Commander Shepard's decisions. Basically, they're saying they're going to do what fans want them to do: give Shepard more choices that actually impact the story, and explain what happened to the other characters after.
Due to a combination of factors, it is unlikely I'll be in the same county as my XBox on Tuesday. Even the prospect of barreling through one of my current saves to get to the end sounds like a slog: Mass Effect 3 is an even darker game on the second runthrough, and I doubt the Extended Cut changes the essential factors of the ending that make it so.
Regardless, I'll have more details when they're available, and feel free to comment below with your opinions on the endings or the Extended Cut.