All those tweets seem to say is "don't worry massive internet outcry by everyone who bought our game, we'll definatly fix it probobly!" which they've allready said (and if their marketing people weren't saying that I'd be genuinely worried about their compotency). I'm also fairly sure they've also said that the ending DLC won't change anything, just explain it more, though it's 2am and I can't be bothered to go find who said that. It's also worth noting that Bioware flat out lies about their games all the time, so the idea that they totally had it planned out this way is kind of ludicrous.
At this point they'd be stupid not to release some DLC to fix the ending, their entire customer base has basically said "we'll throw money at this problem till you make it go away." The problem is that either its something they didn't allready have planned, so it's going to be a crapshoot with standard Bioware writing (see me3 ending) or it's something they DID have planned in which case you just rewarded them money for deliberatly witholding the ending to their 200+ hour game trilogy franchise. I'm 100 percent certain it wont be free, because this is EA and Bioware. They ended the game with "buy more DLC," they have games where NPCs tell you in character "go buy DLC."
Best case scenario is that they'll see all this indoctrination stuff and copy it into the game as a paid DLC. It wont be a good ending, because the indoctrination theory still leaves plot holes and dodgy writing everywhere, but it'll be better than the non-ending we got. Worst case scenario (and probobly much more likely) they'll expand on the crappy ending we allready recieved, since they're pretty adamantly sticking to their guns that this is "art" and everyone allready loves it so there's nothing wrong with it anyway.