There isn't a guarantee how the battle on the roof will progress. Sanji might show up, but it's more plausible he does alongside the other crewmembers, and not all the Strawhats are likely to go up. Nami, Usopp aren't even thinking of going up, Chopper's agreed to nurse the infected and injured down below, Franky's knee deep in a fight with Sasaki on the lower floors. There's also the matter of Onigashima hurling towards Wano. The others are bound to find out, and we may have another "push the Birdcage" for the rest not already in the fight against the Emperors.
The only character guaranteed to meet Kaido later is Yamato, as they have yet to talk to their father face-to-face in the story, and there's still a lot we don't know about their relationship.