If you consider it as a W right now good for you, even though I don't have much of evidences using a bit of intuition and look at where manga Is going in the future Is still enough to understand that his title will be debunked.
Don't be surprised when this happens.
It isn't a coincidence that Mihawk never fought Yonko Shanks or that one of Goroseis is a swordsman, and also not a coincidence that Mihawk doesn't work under WG (the last enemy) anymore, destroying the only chance of him appearing in the final war.