I was ready to patch my game in anticipation of the Extension, I will save my effort because if they will stick with these endings, that are really one, there is no point.
The "endings" are confirmed.
From the mini FAQ
Q: What can fans expect from the Extended Cut DLC?
A: For fans who want more closure in Mass Effect 3, the DLC will offer extended scenes that provide additional context and deeper insight to the conclusion of Commander Shepard’s journey.
Q: Are there going to be more/different endings or ending DLCs in the future?
A: 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.
Q: What is BioWare adding to the ending with the Extended Cut DLC?
A: BioWare will expanding on the ending to Mass Effect 3 by creating 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.
Q: When will the Extended Cut DLC be available?
A: Currently the Extended Cut DLC is planned for this summer, no specific date has been announced at this point.
Q: Why are you releasing the Extended Cut DLC?
A: Though we remain committed and are proud of the artistic choices we made in the main game, we are aware that there are some fans who would like more closure to Mass Effect 3. 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.
Link: Official EA Announcement