If they do it properly I imagine people will be happy rather than upset. As an example, look at Fallout 3. The ending was just horrible, stupid, and didn't even make sense in-universe much less from a story perspective. People complained about it endlessly, and then the Broken Steel DLC was released which "fixed" some of the issues with the ending, allowed people to keep playing, upped the level cap, etc. It's now considered to be one of the "core" DLCs that really improve the game.

So if a DLC actually FIXES the ending, I think people will buy it unless it turns out to be expensive and already on the disk, in which case they'll be enraged instead.

It's a lot like the early stages of Gurren Lagann. Basically, the Reapers don't have the resources to actually kill all of the synthetics, so they try to keep the organic numbers in check for their own good. Like wildlife management, sorta. Except that in this case the Reapers actually probably DO have the resources to kill all of the synthetics, so it just ends up being weird.

I thought they sounded a little familiar. Now I know why.

No, you are right. It doesn't make sense
Also the God Child says something about the creations always rebelling against their creators but he created the Reapers so...

http://www.eurogamer.net/articles/2012-03-19-mass-effect-3-ending-bioware-admits-fans-needed-more-closure

"Mass Effect 3 executive producer Casey Hudson has responded to players upset about the game's ending, admitting fans needed more closure and answers.
The statement comes days after the release of Mass Effect 3: Final Hours, a behind-the-scenes app/documentary. This revealed how Mass Effect 3's ending was once supposed to offer detailed information about the universe's origin, through a dialogue sequence at the very end of the game.
Casey Hudson, following ending backlash, said he and the development team now "recognise that some of our most passionate fans needed more closure, more answers and more time to say goodbye to their stories".
"Your feedback has always mattered," he stressed. "Mass Effect is a collaboration between developers and players, and we continue to listen.
"So where do we go from here? Throughout the next year, we will support Mass Effect 3 by working on new content. And we'll keep listening, because your insights and constructive feedback will help determine what that content should be."
"This is not the last you'll hear of Commander Shepard," Hudson said.
In a Mass Effect 3: Final Hours interview (posted on BioWare's forums), Hudson revealed that forthcoming DLC "would likely happen before or during the events of Mass Effect 3 - not after".
Mass Effect writer Mac Walters explained what the information-imparting ending once was, and why it was decided against.
"You get to ask a bunch of questions and you get your questions answered," he revealed.
"But then me and Casey talked and decided, let's keep the conversation 'High level' - give you the details that you need to know, but don't get into the stuff that you don't need to know. Like, 'How long have [the Reapers] been reaping?' You don't need to know the answers to the Mass Effect universe. So we intentionally left those out."
The ending of the game was not finalised until extremely late in the game's development, Casey Hudson revealed - "right up until the end of 2011".
"One night [Mac] Walters scribbled down some thought on various ways the game could end," Hudson shared, "with the line, 'Lots of speculation for everyone,' at the bottom of the page.
"In truth, the final bits of dialogue were debated right up until the end of 2011. Martin Sheen's voice-over session for The Illusive Man, originally scheduled for August, was delayed until mid-November so the writers would have more time to finesse the ending.
"One night [Mac] Walters scribbled down some thought on various ways the game could end with the line, 'Lots of speculation for everyone,' at the bottom of the page."
Casey Hudson
"And even in November, the gameplay team was still experimenting with an end-game sequence where players would suddenly lose control of Shepard's movement and fall under full Reaper control. (This sequence was dropped because the gameplay mechanic proved too troublesome to implement alongside dialogue choices)."
Mass Effect 3's ending hasn't been the only source of fan backlash. An appealing squad member was reserved for Collector's Edition or paid-for DLC. This From Ashes squad member now appears to have once been part of the main game.
"In March 2011, [Mac] also faced a roomful of Mass Effect developers who expressed concern about hitting the promised holiday release date," said Hudson, revealing the decisions behind the game's delay to March 2012.
"After much deliberation, the CAT mission (or rather, the Prothean mission) had to be removed from the set of tasks. The missions would later be completed as post-release content."
A fan petition for the ending to be supplemented with additional information has now raised over $66,000 for the gaming charity Child's Play.
"We would like to dispel the perception that we are angry or entitled," the campaign's mission statement read. "We simply wish to express our hope that there could be a different direction for a series we have all grown to love."

Guy is an idiot. Looks like Bioware changed their minds at the last minute.

Of course they did. In leaked script everything is the same as in the game and only the most important thing is different. Ending, mainly Reaper's motivation. It wasn't perfect but it was still way better than "Ultimate conflict between biological life forms and synthetic beings".

In leaked script Reapers are trying to restrain black matter from consuming galaxy and they need biological races as source of energy. That's why they harvest advanced races and leave primitive ones to grow (they save them for future). Also that's why suns started to act weird (for example this one near Haestrom). Because of influence of dark matter.

With leaked script ME universe was in way better shape at the end of the game, because it was concluded but also there was opening for more games. Like unknown makers of reapers still existing and biological races had to find way to restrain dark matter by themselves.

Good entertainment if you remember your ME1 well enough: http://social.bioware.com/forum/1/topic/355/index/10279538/1

Why would they throw that away! That sounds great in comparison!

They really need to get some writers with fresh ideas :)

The endings are so similar to each other you wonder why they bothered. I realise they're the studio renowned for the illusion of choice but c'mon... they obviously weren't shy about the finality of the ending, why not go nuts? At least then the 'discussion' would be diluted with 'which was the better ending?'.

Given their earlier foray in the Overlord DLC, and Legion's mission in ME3, the Synthesis ending was underwhelming, that could have been batshit awesome.

Upset fans don't buy DLC. If Bioware choose not to address the ending they'll only be able to focus on multiplayer DLC.

If you've played the ending, where's your motivation for say helping Aria retake Omega (which is situated right beside a relay...) or any other story based (pre-ending) DLC.

That would have been a great ending altough it still goes against Sovreign's "beyond your comprehension." but still a decent ending.

So basically they changed the ending because of the leak and they wanted a surprise?

That reminds me of this picture.

nope that was ending number 29820990810923870129370one the design docs they released really do show ending changes going on till the last second of feature lock

What's 'life is special' about it? 'biological races' may just very well be biological matter, and let it spread by itself with help of mass relays would be a pretty clever way of cultivating it. You know, renewable fuel and all that :D

The ending was awful. The game was good up until then, it had some brilliant weighty choices... all of which meant sweet f-all at the end.