Kaido will have hard time finishing off with Minks and RS. I'm not saying he can't win but he too will suffer some heavy casualty. I bet the Dukes will have some insane Power Ups. Kaido will be weakened down enough for the Supernovas to finish him off, if he actually get in a serious brawl with Minks and RS. He isn't as tough as he is being projected.
The only thing I can't understand is how Big Mom plot will play out. Maybe Peros will convince her otherwise. Kaido himself said Pirates will betray each others..might be a hint..
Alliance has everything to lose here. All their plotting and planning for 20 long years. If they fail to end it during the festival night, more reinforcement from the country might show up. Imagine the state of Samurais when they have fought a whole night. Them failing here can only lead to Impel Down/ Udon V2 which is highly unlikely to happen. Top Dogs of Beast Pirates are yet to show up on the battle. None of the Alliance will make it out of Onigashima if the Raid fails, Kinemon said it himself. The tragedy of Act 3 doesn't necessarily need to be of Raid fail. Oda might be creating a diversion here.