Eh, Law is one of the prominent Supernovas along with Luffy and Kid. The top three so to speak. I don't think Zoro has made it to their tier yet. He'll get there but he needs time. I think Luffy has already surpassed Kid, and by the end of the arc Zoro will probably be close to Law. The problem is how Oda handles Law; power-wise the ope ope no mi can be insanely broken or not depending on what Oda needs for the story.
So, I still stand by the notion that Emna isn't for Law. He cut down Vergo who was a CoA master. Only one who overpowered Law was Doffy and Doffy was a monster that almost took out Sanji. His CoA is pretty good as it is. If anything Law needs to improve his CoO rather than his CoA.
Emna seems more crafted with Zoro in mind. It gives him greater range and power. Something that Zoro really needs if he wants to reach Mihawks level. Remember Mihawk can cut down icebergs, mountains, armadas, and anything else in his way. Hawkeyes has incredible range, precision, but most importantly he has power. Emna is a step in that direction and likely one of Zoro's final swords.