I can't say I don't feel slightly disappointed. Especially with how Luffy was defeated. That being said, all signs were always pointing towards Luffy = Joyboy(despite my wet dream that Nika wasn't Joyboy and Luffy was actually Nika).
That being said, this raises a serious question: Is Luffy actually a reincarnation of Joyboy or does DFs could pass the souls of people who possess the will of the D(or maybe they're literally made out of their souls)and allow them to possess the user under some conditions? Maybe that's why Shanks hates DFs so much and maybe that's why the WG is so afraid of people who possess the will of the D.
It was emphasized Luffy's voice had vanished. This might actually mean he's being possessed. Or...Luffy and Zoro gonna meet in hell confirmed?
It sure looks like possession and that grin, instead of being cool, seems more eerie considering the circumstances.
Maybe this is the bounce bounce fruit and its awakening involves the user bouncing back, stronger than ever. That said, this also might be due to Joyboy's spirit. This shit has so many options.
Actually, I've just seen a theory that the strawhat is n actual DF user...considering the shit that's coming from Luffy's head...this might be it.