Too bad Katakuri isn't coming. I want King vs Katakuri.
Imagine the situation is like this:
Either Big Mom or Kaido actually has own personal agenda and plans to backstab the other. Let's just say Big Mom (that was portrayed as cunning one and backstabbed Germa) is the one betraying the Beast Pirates.
And the betrayal is already happning on the background, the Veterans are suddenly attacking some Headliners. Kaido and his main army don't know about this because they're busy with Luffy's alliance, but somehow King witnesses Big Mom Pirates' betrayal and about to report it to Kaido.
Katakuri, unlike his dumber siblings, actually sees King witnessing the attack and plans to report to Kaido, then intercepts King because Big Mom pirates don't want Kaido to know about this betrayal so soon.
And then the 2 fight. King fights while trying to report the betrayal to Kaido. Katakuri fights to shut King's mouth so that their betrayal plan won't get exposed too soon.