Probably. they have to come up with some way to rationalize why Robin can’t come back to life if he is in fact dead for good next week
It could have to do with the Olympian Crystal, the Magical MacGufin of the week. Maybe the Olympian Crystal has the power to kill a God, so if Hades uses it to kill Robin, then Robin dies in a way that can’t be undone. Otherwise, you’d think Regina would try a heart split the moment he dies.
Dedicating a season to saving Hook and then killing Robin – a good man and father of two young children – in just one episode (poof) is close to being a mockery storywise.
But yes, it probably has to do with the crystal. Hades saying in the promo that he’s not going to “kill” someone, but rather “end” them indicates that something irreversible happens to Robin, and I for one will hate it.