On the other hand, B&B is a really popular Disney cartoon, and A&E might not want to disappoint fan-girls of the Rumple and Belle pairing. So maybe the writers could find a way to wrap up Rumple’s story without necessarily killing him off, and instead write him as having his curse undone by TLK and then packing him off to A Land Without Magic so as to avoid the temptation that magic in SB has to offer. Maybe Rumple’s happy ending could simply be starting over again away from all the crazy once his dark one curse is broken.
Honestly if that were to happen, I could see Belle leaving the show too. If they decide to go back and make Rumbelle endgame, but Rumple leaves Storybrooke, then Belle would surely leave with him.