So, in the future, there will be something Zoro needs to fight that he won't be able to. He'll need a power up. So, what would be that power up? That will go a little bit into Wano. So, I believe Wano is indeed based on the book of Five Rings, whoch is split into five book: Earth: How to use strategy in battle. Water: The training of the spirit. Fire: Battle techniques and how to fight. Wind: Other techniques and traditions. Void: Things beyong human knowledge. So, many people believe in Wano he will train in the Fire Village and get a fire sword. However, I disagree. As we've seen, the Strawhats are exceptions among exceptions. So, wha is the exception among the book naes and purposes? Void. The other ones are about battle, and void is not a commonly said element. But what about him wanting to get a fire sword? Well, I refer you to his fight with Ryuma. He's lighting Ryuma on fire. Where is this fire coming from? Well, in Shinto, Asura demons can control black flames. His flames against Ryuma would represent that ability. Not to mention, it was against Ryuma, a samurai. So, what do I believe is Void style? Using demons and demonic abilities to fight. Zoro trapped the demon in his eye, but he cannot control it. The Curse of the swords like Kitetsu and Kikoku slowly pull the user's soul and will into their Void, thus the village name. While in the Void village, Zoro will see people using cursed objects andhe will apply what he observed in his next battle, where he can control Asura and the flames produced by it.