2 things:
1)Rumplestiltskin’s wife cannot be Cora. Rumplestiltskin was married hundreds of years ago before Cora was even born.
2)Rumple’s wife cannot possibly have a storyline to appear in Storybrooke because she left Rumple before the curse happened and was not immortal. So, unless she time travels, I don’t think we’ll see her.
If the Blue Fairy and Rumple can be hundreds of years old, I don’t see any reason we can’t add Cora to the multi-century club. We don’t know when Cora received her power/magic so we don’t know how old she is. Just like we don’t know how old the Blue Fairy is.