I have no idea what you imagine will happen.
What I imagine is that Zoro is a character who is written to have narrative momentum and cohesion
Zoro’s character is complete when he achieves his dream. That’s all.
There is no plot point that will matter to Zoro as much as this.
there will be no emotional moment that matters to Zoro as much as this
there will be fight that matters to Zoro as much as this
So Zoro’s last fight will be this. It is narratively impossible for Oda to make a better fight for Zoro after this. Nothing about anything after this will matter to Zoro’s character
in your mind you probably think that’s fine. Zoro can basically be a complete character and just hang around to do fights that don’t matter after completing his dream, but I bet even as bad a writer as Oda is even he knows this is non-storytelling