And what if Shanks is the final antagonist and Mihawk is allied with him to be Zoro's final fight? What then lol?
Every other faction (Blackbeard, Akainu, Im) has their swordsmen already (Shiryu, Fujitora, Monk Gorosei maybe), and Shanks has nothing to do with Zoro, so seriously, what would the excuse be then because Benn Beckman is not a swordsman at all.