I believe it is possible for Buddy the Clown to become a Yonko of the sea. Think about it, he already became a Warlord when nobody expected him to, which was recently revoked resulting him to be on the run. He mainly became a Warlord to to his history with the Roger Pirates. After Buggy escapes the marines, I believe it is possible the Buggy will somehow end up in Wano. He will end up in Wano and somehow manage to do something that will result in him accidentally taking out a Yonko or taking the credit for taking out a Yonko. Then he will take the Role of the fallen Yonko upon himself, making him Buggy the Yonko. He will be a Yonko along side Shanks and they can be there together at the end of the series at the One Piece. Just like they promised they would all those years ago when they were still apprentices on Gol D Rogers ship.
Plus it would just be fun to see Buggy in such a role as a Yonko.
Plus it would just be fun to see Buggy in such a role as a Yonko.