Zoro vs King won't happen, unless King somehow makes it to the rooftop. If Oda wanted to make Zoro vs King happening, he could've done it before Zoro helps the fight against both Yonko. But instead, he made Zoro reached the rooftop along with his captain and other three SN. He's destined to fight the Yonkos, and re-open Kaido's wound. The whole fights scenario could change if Flower Capital becomes the location of final fights, though.