If there is anything i dont think Bioware would be retconning at all is Flemeth.
Ever since you meet her for the first time in the Wilds she is obviously written in a way thats supposed to be a mistery that will go on for a very long time.
Even if you dont kill her on morrigans quest (meaning you wouldnt see she can turn into a dragon) she saves the Warden and Alistair by turning into a winged beast and snatching em out of the top of the tower before the darkspawn could kill them (words of Morrigan just a you wake up after Ostagar).
Every little thing about her is consistent since the beggining. You could argue about the appearance change from DA O to the beggining of DA2, because supposedly she meets Hawke not very long after she first met the Warden (I would say there is no more than 1month - depending on how fast the darkspawn destroyed Lothering completely). And then she meets the warden again for morrigan's quest still in her old looks (and this is obviously after lothering and after helping Hawke). Thats the only thing that doesnt add up in terms of consistency, and could be easily explained because of graphics and stuff (2 different games, couldnt make her exactly the same in both) but i think even that has some other meaning. In DA2 they knew about the timeline and that changing her so drastically (whole new body) would look like an inconsistency, so why not just make her look a little more like the Flemeth in Origins? But i think there is a piece of the story there that we dont know about. She was always written in cryptic and secretive terms so they could make sure that throught all the years of story development (games, books, comics, movies, etc) they would still be able to tell her story in the same terms for everyone no matter what World State you have.
I dont think we have seen the last of Flemeth, and I'd bet that whatever way this series ends, she will be right there at the middle, proving us there's so much more in there than we dont know about yet.
And yet, there's still a lot about her that hasnt been answered. We know who she is now sure, but thats not even the most intriguing part about her. Her goal, her objectives, her masterplan, thats the most interesting stuff about her and we still know jack about it. My guess is she's going to be around all the way to the end, mind-blowing us at every turn, and that was the plan from the moment they started developing Flemeth for Origins.
So to resume my answer to you: No. If there's anything being retconned in Inquisition, it is most definetly not Flemeth.