2) A third party takes out Kaido
Or as I like to call it, the Zehahaha Maneuver. I think we all are hoping that other forces are going to show up in Wano, from Marines to SWORD to Blackbeard. The winds are blowing towards a massive all-out brawl, and it wouldn’t be surprising if another party takes advantage of the chaos to move forward their agenda.
This path I find very interesting because in this path I can see Luffy actually losing the battle but still achieving the goal of freeing Wano. In this path, after a long and difficult battle, Luffy could still end up losing to Kaido, the dragon proving to be too much for Luffy to handle at his level. However, here, Kaido would be severely weakened, which would allow for a third party to come in and kill him.
The 2 most likely parties are Blackbeard or the Marines. The difficult part of this path is the fact that the one that defeats Kaido needs to have no interest in conquering Wano. If the Marines do it, maybe a member of SWORD do it(I think most of us could see Aokiji belonging to SWORD, and while I believe that the Yonko are stronger than the Admirals, I could see a fresh Aokiji beating a severely weakened Kaido, especially since we don’t know how much he has grown in the last 2 years): or if it is the actual Marines, maybe their forces are left weakened enough by the war that trying to take over Wano isn’t possible(Because let’s be honest, the WG would love to get control of Wano). Either way, Kaido is imprisoned/killed, Wano remains free.
If, however, Blackbeard is the one to do it, I could see this as the moment that we found out just how truly terrifying he has become in the last 2 years. I could see a scenario were Kaido is weakened, and Blackbeard comes in and absolutely destroys him. Last time we saw Blackbeard fight against a half-dead Yonko, Whitebeard honestly wrecked him. Without his crew there, I honestly don’t think Blackbeard kills Whitebeard. Which is why this would be the perfect moment to showcase his growth in power.
After establishing that Kaido is such a massive threat that Luffy still lost after all his effort, it would be chilling for Blackbeard to come in and utterly and completely destroy Kaido like it was nothing. However, that’s just something cool I would like to see, Blackbeard can come and have a hard and difficult battle with Kaido and barely win. The end is the same, Blackbeard kills Kaido and most likely take his fruit. Now, I have trouble picturing Blackbeard leaving quietly after killing Kaido, but maybe his fight with Kaido leaves him too weakened, or maybe after fulfilling his goal, he simply says that he has to time to waste against Big Mom/The Marines/Con D. Oriano and Zehahahas his way out of Wano.
Another thing I like about this path is that I could actually see a timeskip after it(maybe a short one of a few months), or at least a pretty hard training from Luffy trying to awaken his devil fruit or something. Because this path would show Luffy that he still has a long way to go if he wants to actually become Pirate King. Especially if it’s Blackbeard the one that takes out Kaido and takes his devil fruit. Luffy would need to grow massively to be able to contend.
3) Big Mom betrays and kills Kaido
I can see Big Mom simply abandoning Kaido if it gets too tough, or actively trying to kill him, in either of the other scenarios. Much like Squardo, I think we’ll see a betrayal that’ll turn the tides of this war. Betrayal, Pirate Alliances have been highlighted by Oda heavily. We won’t go this Arc without a giant betrayal (not counting Kanjuro).
*Theory by Tekrow