The best idea I’ve heard yet for Emma and Snow returning, although I know it’s not going to be in this episode, is them flying in on Hook’s ship into Storybrooke Harbor, like they do in the end of Peter Pan.
LOL- Now that would be awesome, but I think they’d have to be there all season to do it that way (unless they weren’t able to make fairy dust in SB at all) otherwise he could just take everyone backwards & forwards as they pleased which would be kind of a let down.