Well there's already many hints on what Oda is planning to do with Kaido
First we know he's related to some kind of experiment, this arc as whole is filled with plotlines related to the most well known experiments, like Sanji, Smile DFs, Numbers, Momonosuke, and if we include PH a build up arc to this saga Vegapunk Dragons, there's also the Kids on PH and Big Mom mysterious case wich we can include in this plotline giving that BM is part of the arc and she form a duo with Kaido, their plot are connected
all these experiments share one attributes, they're all affect the emotions of the victims in various ways, clearly Oda is making a pattern here, what effect the experiments have on Kaido ? this is important since Kaido is probably the most important case, are his powers partly from the experiments? and does his emotions play a part in his effectiveness ? similar to Sanji and Big Mom
Second fate and Joy Boy, there's a prophecy waiting to happen , because it's already destined to by fate, Kaido is part of this dilemma since he care about being joy Boy, seemingly he doesn't think he can be joy Boy, but the problem is what's the reason?
Third Kaido and Yamato, this must lead to something, Yamato for sure will be important to Kaido character, the only hint we got so far is Kaido likes to call Yamato a son instead of daughter implying he wish if she was a man
Fourth why Kaido is in Wano ? what's so special with this place?
Oda will address all these fourth angles, and the answers will decide the plot of the story going forward
all these important mysteries will probably explain each other btw for example Kaido and Joy Boy relationship will be related to Yamato and Kaido relationship, Oda will need make his character coherent, not just random unrelated ideas all forced into one character
and finally Zoro being the main focus of the arc beside Luffy will need to play a part in all of this, this is his arc after all
