If there's something like a Haki susanoo Shanks would flex it at the end of the arc.
Thus, zoro might upgrades his Asura in the following arc maybe even uses it in base like luffy does with G2.
Whatever a Black Blade is capable of, Zoro needs to learn and do something we haven't ever seen another swordsman do on screen. Perfecting asura will be the way.
So, min this arc and the next.