Also, based on spoilers and what Emma herself already said about wanting to stab Rumple with his dagger, I think after Henry course corrects things so that the odds are again stacked in favor of the heroes, Emma will stab Rumple, kill him, and become the next dark one. That will be the big cliff hanger for S5.
Actually according to set reports of that climatic scene in the finale, Emma mentions how the dagger “always needs a name”, and then sacrifices herself. That would suggest that she didn’t stab Rumple, because if she did, her name would already be on the dagger. Either Rumple’s dark one curse is lifted, or he somehow dies without being stabbed.
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