Kaido doesn't have fruit, he is soul linked with BM, he wont die as long as she is alive, and with her fruit it will take some time for her to die of age.That is a thing he owes her.
And targ was never real discussed as Kaido fruit but as Ryu's fruit. If Kaido has a fruit, sea stone would be enough to kill him.
You can imagine soul link like the one from Dragonheart.
You just blew my mind. So you telling me kaido can be an horcrux like Harry potter!!
Best prediction I've seen so far