Kaido will be furious Luffy left Wano, and didn't unearth Pluton. Kaido hated the way the WG ruled the world, and wanted a world determined by war. Kaido would have wanted Luffy to take Pluton, and use it to destroy the WG.
IMO, Kaido wanted to create the new Joy Boy, and set Wano up for Joy Boy to take it over to initiate the final war.
I used to think Kaido would be allies with the Straw Hats if he returned, but if Momo is Pluton's controller, and Momo refused to open the borders and go to war with the WG, I think Kaido will actually flip his shit, which sets up Zoro for the kill. Also, Kaido has just caused too much evil to be acceptable as an ally at this point.
Act 4 Luffy will be Luffy and Big Mom/Carmel's big clash, IMO, leaving Kaido for Zoro.