actually, i'm betting Kakuzu gets killed and Hidan survives. we've seen the weakness in Hidan's technique, but not how to kill him. only how to reduce him to a morbidly comical talking head. it's pretty much established that you kill Kakuzu by getting all five hearts. meanwhile, Hidan lives through decapitation, frequently impales himself and gets hit by Kakuzu's elemental attacks without a scratch. so unless we begin focusing around Hidan again, are they going to just decapitate him again and put duct tape over his mouth? i doubt we've seen all of his abilities too; i don't think slashing someone with a scythe, licking it, drawing a symbol on the ground and stabbing himself constitutes as the "total destruction" his religion believes in. and, as you said, he's in Akatsuki too, meaning he's an S-ranked criminal who's done somthing on par with Itachi's genocide.