Honestly I think both Yonko are going down Oars style. Kaido apparently doesn't lose 1v1 and he has the highest living bounty in the series. Characters, namely the 8 Supernova at Wano, will probably perform feats that lead to the downfall of both Yonko, probably not without additional help from outside forces (Sword/Neko allies).
Not to mention the fact that Luffy or anyone else winning against them solo entirely downplays the future villains/obstacles still left this story has, namely the SSG, Admirals, World Government, Blackbeard and possibly Shanks.
This is why I believe both NEED to go down through combined effort and why everyone prior to this will receive signficant fights to either show off their growth or entirely grow as characters. It's why I believe Luffy will fight the possible Ace and Zoro against King, Sanji v. Queen and Kid/Law/Drake against other higher up pirates (Kaido/Big Mom have tons of them).
THIS is why I also believe characters will perform feats against the Yonko that will eventually weaken them. Zoro WILL get his moment with Kaido by cutting him, and it may hurt him but it probably won't be enough (it may even force Kaido into his hybrid or Awakening, who knows). Sanji may possibly get something at Big Mom considering his history with the character, as every other Supernova/Strawhat may over the battles. The scabbards will have their moments. Everyone will.
But honestly to drive the point home, I dont these 2 Yonko are not going down by 1 or 2 people. It will be a brutal hellhole of a match between several or many people. Luffy and/or Kid may deliver the finishing blows though, that much ACTUALLY makes sense in the context of the story.
And in the end, everyone honestly wins.
