Rumple could easily fix the cup with magic if he wanted to. He was just too devastated.
I don’t know how it will happen for her to fall in love again, but I believe it will. This show is all about believing in happy endings. I have faith. He just has to learn to be patience. The Belle he loves and who loves him is in there somewhere. He need only reach her.
Honestly, I would think it very cruel of the writers if this was the end of RumBelle…that would just make the show depressing.