The only character I can see being killed is Zelena. BC of how irrelevant she has become.
Zelena has a newborn child. I don’t think they will kill her for that alone. Write her off as she goes back to Oz or something, sure. But I don’t see any reason why she has to die even if she is not involved in the story.
I think the biggest bet for a death is rumple.
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"I could have the giant duck as my steed!" --Daniel Radcliffe
Keeper Of Tamara's Taser , Jafar's Staff, Kitsis’s Glasses , Ariel’s Tail, Dopey's Hat , Peter Pan’s Shadow, Outfit, & Pied Cloak,Red Queen's Castle, White Rabbit's Power To World Hop, Zelena's BroomStick, & ALL MAGIC