God all Kaido really needs is a 1-2 chapter FB to explain his origins/motivations (with Rocks) and resolution on Momo being fit for Shogun (i.e. why he hadn't shown his human form yet most likely). That, along with the rest of Luffy's fight and possible Orochi finisher (if he didnt get defeated by the fire) is all the arc really still needs to accomplish before closing chapters. Max that's like another 5-10 chapters imo (basically this next volume). Sure, there will be another 5-10 chapters after that to close the arc, as there always is (i.e. Kin reuniting with his wife, Zoro visiting Ryuma's grave, big revelations outside of Wano, the recovery/plot moving chapters, etc).
But....50??? Lmao. Arc has max like 20-25 left and that's being generous imo.