I don't know why devs are so scared to just pick a canonical ending and move on with their lives.
I just don't care, sorry. Whatever makes for the better sequel and better story is fine by me. For example the Morrigan ending of Dragon Age: Origins is super interesting, yet they can't do shit with it because it was one possibility among many.
If you treat the story of maybe games in general as a bit of co-authorship between the game developers, creators of the medium and all its possibilities, and the player, author within that medium; then I think it safe to say that one facet of each genre is how much freedom there is between that 'pact' - some focus on a guided experience and others, one might call them RPGs, try and accomodate the player's creativity. In shot, some are Avellones and others are most everyone else, while Gaiders themselves are in-between: its not that player choice isn't rewarded somehow, but its a sideshow - an 'illusion'.
All this babble is to say this:
BioWare has absolutely no business choosing a canonical ending for DAs simply because your choices weren't ever supposed to matter all that much. Just as they are minor permutations of a similar story
within Origins, they are going to be minor permutations within a DA franchise. And Morrigan's is no different. The only reason why they didn't tackle that in DA2 is because the whole affair would look like this:
When a more polished version may just not be much better than this:
Make your choice, Inquisitor/Grey Warden/Joel from Last of Us. Don't look at me, I'm just a sugar coated plot device.
Really, DA has been about telling a story while paying lip service to past permutations. That's it. And it sounds good on paper too: if you killed a given character, he's absent, if not, he appears out of nowhere to give you a sidequest. If you had the Old God baby, then he'll be there, taking his role in a larger story about the dragon Old Gods who may or may be related the Return of the Burning Legion from beyond the NetherVeil into the unsuspecting world of Thedamriel.
Shit happens when the writers start to think they need to choose a canon ending. When, instead of just making a new character, they insist on elevating the role of a major character to that of 'universal' importance. Leliana, a major but killable NPC gained a DLC all about her so that the players could 'bond' and forget that her schizophrenic carebear face could be slain at any given point.
This is marginally better than what Blizzard does with Warcraft, where 'fan-favourites' are resurrect (in the style of Superman et al) all the time because, and I paraphrase, its hard to make people care about new characters. But its still counter-productive because its arbitrary and its prone to retconing things, which while not unavoidable shouldn't be done lightly. Much less like its something the writers are entitled to.
When you say that you 'don't care' and 'whatever makes for a better story is fine by me', you're being contradictory. If you don't care about retcons, it means you don't care about what was good so far. Indeed, when things are like this, nothing stops someone at the staff room from just having this great idea about how Anders and Morrigan, apostates extraordinaire, should join in the apocalypse and even become a couple. Boom, players can keep their silly headcanon and we move on with our lives.
In fact, you sound like a particularly bullshity biodrone from the BSN, who would keep repeating 'I don't know what you're talking about, BioWare's doing a great job to me because, so far, I made the
right choices'.