I just had a shower thought… Oars’ Giants Race is officially named “Ancient Giant”.
I assume Kaido to have this Ancient Giant Race’s blood and hence he might be some kind of last survivor of the species. Maybe Kaido is half Ancient Giant half normal Giant, which explains his appearance.
Now We know that Big Mom wanted Elbaf’s powers by making an alliance with them, also she basically wants to subdue them. We don’t know Kaido’s plans yet, but what if he also plans to take over Elbaf as some kind of “righteous heir”?
In this theory I think both Big Mom and Kaido will survive Wano, Wano will just tease both characters and both characters will end up in an Alliance. It could be that they flee from Wano and move forward to Elbaf. THIS is the moment Blackbeard invades Whole Cake Island and moves forward.
With that Kaido and Big Mom will take over Elbaf and subdue the Giant species.
I think Elbaf will be the arc where we will see Shanks and Blackbeard might also jump in. The grand finale of the Yonko saga.
*Theory by Rej