New details suggest that response to the DLC could be mixed, depending on why frustrated players were let-down by the current endings, as the Extended Cut will reportedly focus on fleshing-out the endings with new “variations” - dependent on the player’s choices over the course of the series. That said, the DLC will not include new gameplay sections or choices.
According to Kotaku, who was contacted by a spokesperson at BioWare, players will be able to access the new, and more individualized, ending content by loading-up a pre-end game save file - which will contain the necessary data for the updated game to present new ending “variations”:
News that the extended cut won’t allow for decisions, and instead will simply deliver a more personalized conclusion, should satisfy the host of gamers who, after watching their respective Mass Effect 3 ending, still wondered about the fate of their favorite characters - as well as larger plot implications (such as the Mass Relays, etc). However, players who were hoping for an entirely retooled ending that actually allowed for more choices (such as the involved progression at the end of Mass Effect 2), could still be pretty underwhelmed with BioWare’s Mass Effect 3 finale 2.0.