Oda already found an answer to that.
It is not simply because Luffy's punch are stronger that he will beat Kaido.
It is because 14 different people jumped him, he learned to do internal damage and now he can even coat his attacks with his Conqueror's spirit.
Luffy won't beat Kaido because his punches are stronger but rather his will and Conqueror's spirit will somehow overwhelm Kaido and not only that but Kaido also would be taking attacks for the past 30/40 chapters till his defeat.
If it weren't for Luffy's massive conqueror spirit he wouldn't be able to clash so casually against an hybrid Kaido while in Base who more than likely is at least 10x stronger than him.
So Luffy will beat Kaido because his will and Conquerors spirit will be bigger than Kaido's (while not ignoring that Kaido has been sustaining damage for the past 25 chapters and will sustain way more damage until his final encounter with Luffy), this is a Arc where Luffy becomes a worthy King just like he became a worthy Captain in Ennies Lobby.