The free downloadable extension to Mass Effect 3 will beef up the game's current ending, but it will not include ending or change what happened in the current one, the game's creators said today.
That information comes from a new post on the official blog of Mass Effect studio BioWare:
Are there going to be more/different endings or ending DLCs in the future?
No. BioWare strongly believes in the team's artistic vision for the end of this arc of the Mass Effect franchise. The extended cut DLC will expand on the existing endings, but no further ending DLC is planned.
The "mini-FAQ" reiterates that the winter-scheduled DLC will add "additional cinematics and epilogue scenes to the existing ending sequences. The goal of these new scenes is to provide additional clarity and closure to Mass Effect 3."
The studio says "the goal of the DLC is not to provide a new ending to the game, rather to offer fans additional context and answers to the end of Commander Shepard's story."
MASS EFFECT 3 EXTENDED CUT [BioWare Blog]