If we’re going strictly off of potential foreshadowing from the actual plot, the character who has been alluded to as dying is Hook. (1) Emma called him dead guy of the year in 2×13 (2) Hook and Peter Pan have both claimed Hook excels at surviving (which suggest one day, fate will catch up with him) and (3) Emma called Hook a ghost in 3×12. Also, Hook is lying about something. Why?
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"That’s how you know you’ve really got a home. When you leave it, there’s this feeling that you can’t shake. You just miss it." Neal Cassidy