I answered this. There will be no more new endings. I used the "quotes" as we consider the Extended Cut the ending, the finale, the stop whatever you want to call it of the ending of Mass Effect 3. We do not plan to make new endings, give more closure to the endings, adding or subtracting to or from the endings, etc. We are done with the endings.
That said, we are working on some very cool downloadable story based single player content. In these DLCs there will certainly be elements that will effect the end of the game. As Mike Gamble already said, depending on what you do in Leviathan there will be new dialog with the Catalyst at the end of the game. These sorts of elements are definitely possible for future DLC as well.
And for all those stating "Well if you don't X I am not going to buy another game/DLC/etc from BioWare again". I'm sorry you feel thht way, but I understand it. That is your ability as a consumer. If a company (us, a burger joint, a shoe store, etc) does not live up to your expectations, you go elsewhere. I get it and I do the same thing. I do not fault anyone for feeling this way. Hopefully, the DLC we come up with or a future BioWare title will make you want to give us another try.
However, if you don't like it, feel free to leave. I'm sorry we have disappointed you and as I said, we'll try to make better content or games in the future that you will hopefully enjoy. No one if forced to be here. You don't like it, feel free to take your business elsewhere and stop trying to ruin the funn and enjoyment for those people who do enjoy ME3 and the DLC.
Done now.
LOCKDOWN!