*sigh* just so you guys know, you're proving the homophobes right.
"Once we have gay marriage/relationships, what's to stop marriage/relationships with multiple partners! Blah, hate, hate, hate, blah."
^
Not my opinion, I just don't like seeing people like that have any legitimate reason to say they were/are right.
I doubt polygamous relationships will be occurring in Dragon Age. Mostly because:
A. They'd be too easy to fall into. People have enough trouble falling into unintended romances(I'm looking at you, Anders!) Imagine someone who did not want to have multiple romances(but wanted to flirt to see the ensuing drama) suddenly find themselves in a relationship with both companions. Awkward. It would be a good learning experience for the player, though. You never know how open-minded a person you flirt with can be. Not open-minded enough, and sometimes, TOO open-minded.
B. Require far too much in the way of resources to meet the demand for such content. A one-off threesome is one thing, like with Isabela in DA:O, and again in DAII. But to make it a full-on relationship, you'll need a great deal of dialogue and additional cutscene work to make that kind of content good. And Bioware does have high standards for this kind of thing. If they can't make it good, they won't do it. They made that mistake with DAII, and look what happened.
C. It would be more difficult to provide for that situation in the epilogues, and latter in Dragon Age: Next. There's already so much in the Keep. We don't need to include a set of plot flags like that, making additional flags for each character and different dialogue when/if you meet them again.
I mean, put it all together, they might as well make another romance entirely. And in the end, I think that would please more fans than adding polygamous relationships would. Personal opinion there, with little to back it up in the way of facts. Come to think of it, you can say that about my entire post to this point. Regardless, it's where I stand.
Plus, from personal experience, I've seen polygamous relationships between people I know go up in smoke. Open relationships and even swinging I've seen succeed to some degree, but polyamory, not so much. They just never seem to end well for anybody. Normal relationships are hard enough to maintain as it is, with the feelings of two people to account for. Adding another person into the mix just increases the chance of the whole thing blowing up in everyone's faces. This something I have personally observed, not just conjecture.
So the devs have to create not just one but two NPCs who are not only ok with a polygamous relationship to start with, but don't subsequently develop issues with such an arrangement. This, I think, would be too hard to do with the kinds of complicated character Bioware creates. They would have to have two characters developed specifically for this kind of thing. And Bioware had already said that they create the character first, make them fascinating in their own right, before they determine their romance status, if any. Then they have to invest the resources for such an outcome to occur, and will have to provide for that play choice for as long as they import the previous decisions of the PC.
I don't see that happening.