It would be super fast character development but I think I’d prefer that to everyone going back to the status quo which was my fear about an AU in the first place: no lessons are learned because the board is reset at the end.
That’s why I hope that we’ve been watching the AU all along, and that we and the characters are going to get a glimpse of how they would have been in the prime universe. I think their lessons would have more of a lasting impact that way.