Oda won't make a SH character kill another character just for revenge.
He doesn't even let villains kill other characters outside of flashbacks.
This ZKK fantasy has always been a pipe-dream.
Many supporters of this idea don't even understand that Zoro killing Kaido would actually be a victory for Kaido, since his one dream is to die in a glorious way, like Oden did. This was literally established with Kaido's introduction, where he tried to kill himself.
That's the most obvious reason why Kaido won't die by a SHs hand here: Oda won't grant him his dream.
He doesn't even let villains kill other characters outside of flashbacks.
This ZKK fantasy has always been a pipe-dream.
Many supporters of this idea don't even understand that Zoro killing Kaido would actually be a victory for Kaido, since his one dream is to die in a glorious way, like Oden did. This was literally established with Kaido's introduction, where he tried to kill himself.
That's the most obvious reason why Kaido won't die by a SHs hand here: Oda won't grant him his dream.