Something has to happen because I don't see the Elbaf force getting wiped out by Imu at this point. We're in the end game, narratively, so loses like that are not to be expected anymore.
I'm not looking at it from a powerscaling context at all. No Ls or Ws. Just saying that something needs to happen that will put an end to the fight and forcr Imu to withdraw.
Whether it's a character, a macguffin like Joyboy's haki again, something happening in Mariejois - Imu will not defeat them here.
Though he will have the upper hand for sure. I doubt anyone even injures him at all. It will be a showcase of power but the SHs and Elbafians won't be defeated.