I think Zoro and Sanji will join Luffy. Luffy should be VERY tired by then and so should be Kaido. The monster trio can attack with their ultimate attacks all at once and that'd result in Kaido's death. He'd have to deal with the intenal damage from Luffy and the burn and internal damage from Sanji. Therefore, I believe Zoro will be able to kill him and then promptly collapse, almost dead.