I think that Oda might have Big Mom soon fight all of the SHs together in order to serve as the SHs “warm up” fights and to show the crew all working together for the first time in a while. I expect that during the fight, Nami will steal Zeus back, either Nami or Sanji will steal Prometheus, and maybe Brook will steal Napoleon. At the end of the fight, Luffy will finish it off by using a powerful G4 and Ryou attack to her head, similar to how Luffy beat Oars with a powerful G3 attack to the head. However, this won’t defeat her in a conventional way. Instead, it will revert her back to O-Lin, thus making her peaceful