I just re-read last chapter and noticed something: Kid seems to be too fresh. We know that Law is out of the fight already but hear me out there is no way that the Yonkou is defeated and Kid is left with energy. If you look at everyone else's fight, everybody passed out or was unable to continue combat: Law, Zoro, Sanji, the dog and cat. They were always talking how they had no energy left, but this hasn't happened with Kid yet and he's seen smiling with his last attack... he recieved no damage this last chapter!!
Big Mom, very damaged, is gonna stand back for a last round 1vs1 against Kid. She's gonna show her final real powers, and Kid is going to defeat her with a more powerful version of assign that will attract all the bombs that Yamato is dealing with through that hole Law created.
If you remember Law asked Kid for how long he can keep the magnetism but Kid refused to answer. This is his real final card. All the explosives and huge swords are going to pierce and fuck up Big Mom, finishing the fight with a huge explosion destroying like half of Onigashima.