Hook chose to stay in the Underworld when the Orpheus and Eurydice-plan went bust. Do you think he’ll actually stay dead/down in the Underworld? If not, how else can the heroes get him back?
This one is a no-brainer. He will not stay there for good. There will be some magical loophole that will allow Hook’s soul to re-enter his rotting corpse (sorry for the description, just trying to remember what Hades said) and for his body to be revitalized and reanimated with his soul in it.
It might be something to do with a reward from Zeus for his tremendous sacrifice etc etc.
Here’s what I think will happen. Zeus will find out that his brother is up to no good, and will team up with Hook to help our heroes. The press release kinda hints at that possibility. Zeus also finds out that Emma and Hook passed the true love test for the ambrosia, but that Hades tricked them. Therefore, Zeus gives Hook some ambrosia after Hades is dealt with. A literal deus ex machina.
Or this. Probably this.
Keeper of Regina's bravery