He wouldn't necessarily have to be Peter Pan (though it would explain how earnest Bae became the thief Neal). OUAT often supplants a primary character with a secondary one. So like Jack the Giant Killer became disposable, Peter Pan may not be a central character, but a secondary one with Bae being a Lost Boy (which he sort of literally was) who eventually made it to a more mundane world.

He could be Peter Pan though. I still remember the large group photo/promo at the beginning of the season showing Henry dressed sort of Peter Pan-like and the writers saying that the wardrobe choice would make sense later.