With the War starting in the next few chapters (Hopefully). Even with Jinbei joining the fray, the combined forces of Kaido and Big Mom seem insurmountable. With the Calamities, Flying Fighters, and the strong members of the Charlotte family Big Mom brought to Wano, the Strawhat Alliance forces are outmatched in terms of strength. So there are a few possibilities all of them with there own pros and cons, to even the field.
1) Something needs to happen to Big Mom before the confrontation.
Kaido is the main focus of the Arc, and he's the one everyone is gunning for. Even with Three Supernovas (Luffy, Law, and Kidd) that still won't be enough. Having the Group either split up even more is just a losing situation for the Allies. Taking Big Mom out could be as simple as making her Sleep during the War or something.
2) The Marines/WG show up.
This is one of the more popular Theories. Having an Admiral there to fight either Yonko, fighting Big Mom for the War or Fighting Kaido weakening him to the point where either Luffy can deliver the final blow or the Supernovas together can. Maybe we can see some stronger Vice Admirals and even some CP0 agents fight some of the Charlotte family. So that the alliance can focus on the Beast Pirates.
3) Nekomamushi bringing the Whitebeard Pirates.
While this is the one most likely going to happen. The big thing is how much are they going to do, when they arrive? This one really depends on at what point they join the War at.
1) Something needs to happen to Big Mom before the confrontation.
Kaido is the main focus of the Arc, and he's the one everyone is gunning for. Even with Three Supernovas (Luffy, Law, and Kidd) that still won't be enough. Having the Group either split up even more is just a losing situation for the Allies. Taking Big Mom out could be as simple as making her Sleep during the War or something.
2) The Marines/WG show up.
This is one of the more popular Theories. Having an Admiral there to fight either Yonko, fighting Big Mom for the War or Fighting Kaido weakening him to the point where either Luffy can deliver the final blow or the Supernovas together can. Maybe we can see some stronger Vice Admirals and even some CP0 agents fight some of the Charlotte family. So that the alliance can focus on the Beast Pirates.
3) Nekomamushi bringing the Whitebeard Pirates.
While this is the one most likely going to happen. The big thing is how much are they going to do, when they arrive? This one really depends on at what point they join the War at.