Ughhhh hard to say if jimbei is going to join them. I mean a while back didn't they release some collectors coins in japan with all the strawhats and jimbei as well? Pointing heavily that if the marketers and licensees know that Jimbei is going to be part of the core crew maybe it's something oda's intended for a while.

He could do the whole ohhh jimbei's dream is to promote tolerance for fishman across all of the seas. Other then that I can't think of any good reason why he'd leave fishman island behind. Especially in wake of the recent civil war seems like there's even less reason for him to leave. He has about as many reasons as Vivi did to stay behind.

Although if he does join he'd probably be the most powerful new recruit. Might even shake things up in terms of the Monster Trio Hierarchy cutting sanji out of it.