I actually do think Rumpel is a little afraid of Cora. He knows what she’s capable of, and the fact that she’s so hell bent on coming to Storybrooke is a bad sign. So, I don’t think he’s simply afraid of Cora changing the rules of the game. There are people that he loves that could be at risk. For all he knows, Cora could hurt Belle or slow down his search for Baelfire.