Gilad Pellaeon

There's almost no chance of anything set after 3H unless it's thousands of years later à la Awakening. Prequels, yes, but Fódlan has amazing worldbuilding. I don't know if Dagda could measure up. Or Almyra. At this point, I think the world is dead and buried.

A canon ending is just an ending that is the one that is chosen to continue the narrative. Not that any of the current routes aren't capable of being declared canon, just that generally there isn't a declared ending when they are all so radically different. To put it another way, if in the Knights of the Old Republic game back in 2003 the Dark Side ending was declared the canon ending, it means that the following games and universe would treat it as such. That would obviously not be a "happy" ending, but just the ending. So if they remade SS to be the canon ending and had Edelgard play the villain and have her die at the end, I would not consider that a happy ending, but it would be the canon one. Currently, the AM feels the closest to a canon ending because not all the other house leaders are killed. Another example I just thought of is XCOM2, in which you lose the first game. The canon path of the current XCOM universe is that the player did not win in XCOM1. That's why I would have advocated for a more nuanced route that combined them all, because almost all of the routes could have been combined if the leaders had talked to each other, because in general, none of their goals are even opposing. All want to destroy Those Who Slither in the Dark, intentionally or otherwise, all want a better future for Fódlan, and the issue between them all in their past hurts and their inability to trust others. Even with a canon path I don't think you need to imply that the morality espoused there is per se the correct one. You could even have options where Byleth openly disagrees with the chosen path, but for moral or ethical reasons can't join the other side either. If you keep Edelgard the villain, Byleth may just find it more egregious to work with TWSitD than Rhea and crew despite them also being flawed.

The entire point of the game was that you cannot have a singular end to media? Because I really doubt that was IS's entire thesis here. I'm not even saying that you have to have a happy ending, but I really don't think that any of the current 4 endings are the canon one.

VW and SS are basically the same, with VW needing minor tweaks and a changed final boss to Rhea over Nemesis, but is otherwise much closer to a finished product than SS. CF just need to have more to it. But reworking and remaking SS from the ground up into a more "correct" route would be the most optimum solution to me, as Fódlan has a lot going for it, but with 4 radically different endings, we won't ever see this world again. Tellius is and was my favorite world, and the hints that this might share a glove with Tellius would be great if IS could follow up on it, but they can't.

And I truly wish they had opted for more of a Revelations "true path" for SS as DLC over what we got. The Cindered Shadows was a real let down as a DLC for a few reasons, and I wouldn't mind it if it wasn't the only story DLC. I really do love 3H, but the game is plagued with some puzzling flaws and a solution that seems obvious to me. SS needed to be cut and reworked. That would allow for more time for CF and for VW to be worked into better states than they are in now. Edelgard and CF is my favorite route, but AM is the only route that feels complete and fully fleshed out.