I really hope we see her again. I would love to see her back story.
Since we know she was "the daughter of a miller" and the original Rumpelstiltskin story is about the millers daughter, I'm sure her back story will have some similarities to that tale. However in that tale the Rumpelstiltskin helps her spin straw into gold which leads to her marrying a king, and this price is her first born child. She ends up beating him by figuring out his name. Obviously that isn't what happened but I'm sure Rumpelstiltskin has something to do with Cora and her powers.
My theory is she somehow got his dagger.
As for the queen of hearts, that would be awesome.