One spot: Charming’s dad which opens us up to Camelot next season. I do believe he was a knight in King Arthur’s court.
Second spot: Rumples mother. I say this because this will finish out the Rumple backstory and leave room for him to develop as a character with the present and close out his past.
Still want WWW to be Mals sister as I believe it to be a bigger plot driver than Regina who is the epitome of an only child.