Only way Zoro leaves the crew is if Luffy himself chooses to disband it, and that is already unlikely as Luffy loves adventure in general and would probably try to find something even harder than the One Piece to continue adventuring.
But on the chance he does, I just do not see him adopting Mihawk’s lifestyle. The two aren’t that similar, and Mihawk’s lonely life at the top isn’t idealized in the story, rather he gained companionship and even started understanding the value of fighting for someone other than yourself.
Plus Zoro, someone who helped fill Luffy’s heart from loneliness, would be counter intuitive if he adopted a solitary life.
Dojo master Zoro is the likely outcome for him if he doesn’t continue to travel with the Strawhats.