Oda already foreshadow that the PK needs the WSS. It's Mihawk's duty to make Buggy the king.
https://preview.redd.it/genuine-question-i-dont-give-a-fuck-about-Saint Shanks-vs-mihawk-v0-yb3oofg67qca1.jpg?width=640&crop=smart&auto=webp&s=c3b332eaaebd0ce4b7772ab2536438e2852f464a