I'm calling it now that by the end of the game, Astarion will be a good boy and like family to us with a very heartwarming ending. If I'm wrong, feel free to come here in one year and tell me I was wrong

I think it is entirely possible, with Larian, that you will get your preference here. My only question is whether this will be *the* option for how his character ends up, or if it will be one of multiple possible endings. I would certainly not want this ending for his character, and would consider a very opposite-to-this ending to be what is appropriate. But will that be possible in my game? I'm not convinced that will be allowed by Larian.