I was strongly in favor to IT, and I still wish it was true- but quite frankly after Extended Cut and everything post-ME3 ending just seems to indicate that it's indeed over.
From even a business perspective stand-point, it feels really questionable to add what-would be, the real conclussive ending several months after it's release. You'd have lower playerbase then during the first week or months of the initial playerbase, people do move on and tend to forget/ignore what is to come.
The ending just seems to give you clarification what actually went down, and given the "showcase" of per se, Synthesis- seems to indicate that this is what happends, and nothing really else. The half man, half machine theme seems to be just influenced by Deus Ex and whatnot, and they forgot the players real goal, which was to stop the Reaper threat, not somehow merge with their technology and etc; (Okay, not really merge- but the whole co-existance with what has been reaping civilizations for aeons seems really out of place, which I believe is one strong arguement for why people are abit upset over the whole outcome, seeing as 2/3 possible endings are co-existance)
Either way, the extended cut work-with the music from Sam Hullick seems really composed in the matter to give you the real-feeling of satisfaction + conclussion. I believe the Memorial Wall and the Normandy flying away is a pretty good indiciation that, this is the end of the story, now you can use your imagination for what happends there-after, not deliberately feeding the player with the makers vision of what happends.
I believe that's also what the original ending was suppose to accomplish, however- people really wanted the after-math effects (Which was pretty much given by the makers of ME3 again, the baby-krogans and all pretty much self-explanatory event that you went through ME).
It doesn't seem to give the players that much of an "Hmm, I feel there's more to it, I mean- all these scenes I just saw for the past 5-10 minutes seems shady!" -> I wouldn't exactly call the Memorial Scene anything "Indoctrination", alá thing, it just feels like that the team does indeed, mourn the loss of their love- or Commander, and they're going to move on afterwards.
Destroy just gives you feeling that, they do know Shepards probably out there alive- which of course is hinted towards in the added scene with Shepard drawing his breathe, but again- it's an question of interpretation if it might be even his last breath before perishing, nobody knows- it's the players decision to give you the ending you want, not what the maker wants. I feel it's also somewhat justified with Biowares decision, as much as I may dislike it, because I've got abit of a lack of imagination in this regard.
I doubt they're going to pump more of their budget and work onto additional ending scenarios. It's alot of work and variables they're going to factor, let-alone- it might even cost you money, if it indeed does come out, considering they've got a limited budget- eventho they're a big name. They're not going to carry out free-DLC forever, it's just a retcon from the backlash from the first few month of hate to win back some paragon points from the community.
If it does indeed contain some added ending-scenes and scenarios, and there's a pricetag- people are going to be quite upset over the fact there's more to the ending content, but only accessible with DLC. That's like paying for a book, and you don't get the last few pages from the Author, you need to actually buy those pieces for a sum, yet- you can feel conclussive with what you've read. It's a decision, but the ones that are die-hard fans, will end up being abit mad over the fact there's more to it, but there's a fee in order to access it.