kuzan wont leave soon
he will stay with them till they get defeated. most likely actively contributing to their defeat.
he will be the iceberg that sinks the titanic
I think Kuzan's true goal is keep both pirates and the WG from finding the One Piece, or using it.
Kuzan realized the WG would never let him actually chase after the one piece as an admiral.
So he became a pirate.
Kuzan seems to be part Garp part Sengoku.
I think he knows from sengoku that once the treasure is found, the final war really will start.
I really want kuzan to actually be teach's ally, though.
Ohara scarred Kuzan. Learning about blackbeard's experience on god valley would most likely make Kuzan feel legitimate sympathy for blackbeard.
Let's be honest.
Is there anything blackbeards doing that's actually worse than what the world government is doing? Like anything?
Blackbeard is definitely a lot more evil than Rocks, but I could see Kuzan being like "Hey, Teach has a legitimate point and is more rational than Luffy and so much less evil than the celestial dragons.
There's also the possible relation between Eris and Robin, here.