I think we can all agree that Morgana is at the point of no return, and even if she wasn't she wouldn't want to be good again, but if you read the Arthurian Legends (like I did) then you would know that before Arthur's death, Morgana and Arthur reconcile.
I mean, I know Morgana is as bad as anyone could get, but if the last 10 minutes of the last episode of Merlin is an epilogue, do you think the writers will stay true to the legends and have her and Arthur reconcile, even though the writers aren't exactly the best to sticking to the legends?