The only problem with the Beauty and the Beast idea, like a few people have said, is that it would happen REALLY fast. It would mean that Belle would have to fall back in love with Rumple in about two episodes (since we know Rumple is looking for Bae in at least “Tiny” and “Manhattan”) Plus, if they do it now they could never do it again, because it’s a very emotional thing that I think would only play out once to be effective on the viewers. So I like Phee’s suggestion that maybe because magic is different here the dagger won’t work in the same way.
Also, I’m not sure I like the idea of them killing Cora in this episode. They have so much story to tell: her connection with Rumple and I think they have to tell us more about her time in Wonderland, not to mention where her heart is and how many lands she’s been to and if she made alliances there (she told Hook she has traveled to too many lands to be stopped by Emma/Snow) I can see them taking Cora to the either the penultimate or season finale.