Don't hold your breath. If ending DLC is released it will be because Bio has been scrambling the past couple weeks to throw something together with the most popular fan theory rather than something that was planned out in advance.
Even that would be better than leave it like it is though.
If they actually had something like this in the works the PR machine would be tripping over itself to reassure people to just hold on rather than the current focus of "We're listening to your complaints and we're collecting feedback".
For some reason I feel like they WANT people to go all hurr durr about the ending. And then drop the bomb later.
But who knows, let's see what happens.
I agree on your first point.
As for the second, you're half right. They want LOTS OF SPECULATION about the ending. I don't think they thought about the second portion.