I think if Kuma sees Luffy in Gear 5 before dying and getting to say goodbye to Bonney before dying, that would be a really great way to tie his story together.
My main issue though is if they manage to have Kuma return to his original self for good, then I think that it sorta cheapens the emotions that this backstory made us feel. Like, how much less impactful would Rosinante's death be if he turned out to be alive again at the end of Dressrosa? I think Oda did a really good job at making Kuma's/Bonney's backstory a strong emotional gut-punch, but I also feel like that gut punch was sorta be undermined on rereads if they manage to bring Kuma back
My main issue though is if they manage to have Kuma return to his original self for good, then I think that it sorta cheapens the emotions that this backstory made us feel. Like, how much less impactful would Rosinante's death be if he turned out to be alive again at the end of Dressrosa? I think Oda did a really good job at making Kuma's/Bonney's backstory a strong emotional gut-punch, but I also feel like that gut punch was sorta be undermined on rereads if they manage to bring Kuma back