The only ones i'm practically sure will fall first are
- Killer should be the first to fall. He has the least portrayal out of them, was also unsure if they could have won in the first place. Besides i think Killer might be used as a motivational boost for Kid
- Law might fall next. I think he'd play a bigger role than Killer, but it'd limit to doing some surgery hax to Kaido before being defeated and leaving everything else to Luffy. And considering his ultimate ability affects things from within, Oda might even relate it to this battle, in which case it's even possible he might die, but i hope to be wrong
After this, it's debatable between Zoro and Kid, because of Big Mom. If Oda aims at Kid doing something to Big Mom, Zoro might fall first, with Luffy and Kid doing their ultimate combos against Kaido and Big Mom. However if Kid's destiny remains against Kaido, it's debatable. I could see Kid doing some ultimate tandem with Luffy after Law got defeated, before falling himself, in which case it would depend if Zoro would fall inbetween before his final act of scarring Kaido with Enma or not
Luffy on the other hand will be the one to outright match and beat the weakened Kaido