The big problem with black blades is that we've known them since day one, we've seen how Zoro performed with one, we've seen how Mihawk performed with one and so far they haven't been impressive at all. And this all probably comes from the fact that "black blade" as in permanently black weapon wasn't a proper concept until very recently; in other words, odds are Mihawk's sword was designed as black just for the sake of his theme since black armament wasn't a thing until post-timeskip (we can apply the same to Ryuma, in fact, who also comes from a "darker" design theme) and even in Dressrosa it didn't feel like Mihawk was talking about black blades in an impressive way ("every blade can be a black blade if you apply haki", basically).
When it comes to actual feats, Shusui was indeed hyped by Zoro as having a higher destructive outcome and hardness, but this wasn't something new: Wado Ichimonji was hyped as the only sword to survive the clash with Mihawk, Sandai Kitetsu was very sharp and bloodthirsty (Zoro had problems to subdue it to his own will) and Enma has been consistently emphasized as somehow special (starting by the fact it can suck haki by itself). And regarding Mihawk, he still required the breath of things to slash a weakling like Bonez, something required with any regular blade.
The picture I get from this is quite messy because Oda hasn't really made the black blades any more salient, any more special than regular swords: Mihawk still needs regular swordsman techniques and his Yoru wouldn't break Wado, and Shusui was just one more sword in Zoro's progress (Sandai was hard to master, Shusui was hard to master, Enma was hard to master). Will Oda retcon this to add new abilities? Who knows, he could follow this path but he could also treat it in a more symbolic, philosophical way; show with it that the swordsman fully connected with the blade; or even make it a proof that the swordsman who left his will permanently in his sword achieved with it the pinnacle of the strongest swordsman, which ultimately is about cutting everything but nothing at the same time.
We will see.