Luffy will beat Kaido because otherwise it would be disappointing for the fans. By the way Luffy wont make Kaido faint. Why? Because...Rocks will return,and will show up in Onigashima! (Or Wano). And,listen listen,Luffy will fight together with Kaido and Big Mom against Rocks!
Rocks is a big character and kinda like the Madara Uchiha of One Piece. God Valley disappeared completely,how is that possible? It was probably transported to another dimension,together with Rocks. Well,now Rocks will return,but,as we will learn in the Kaido's flashback (that will start right after the appearence of Rocks) he wont be in a good relationship with Kaido and Big Mom,so they will fight on Luffy's side against Rocks! Absurd theory i know,but i wanted to write it lol.