> Later on, during Zou, Oda foreshadowed diamond’s durability once again through Pekoms, who was surprised someone as carefree as Luffy didn’t react to it’s durability.
This to say then, that Oda at multiple occasions already hyped and foreshadowed the diamond toughness as a great challenge.
But when exactly we’d see that challenge?
> There had been theories that Shiryu would eat Jozu’s Diamond Devil Fruit as a challenge against Mihawk, but Oda decided to give him the Suke Suke no Mi (invisibility df) instead, rendering that possibility null.
So now the question is, what is the point in Oda hyping the diamond durability if we never saw it as a challenge in the future? And Oda isn’t the kind of author who makes foreshadows for nothing. For this reason then, I do think the diamond challenge will come back to fruction at one point.
When exactly is unclear, but there has been another weapon that Oda hyped, yet we still don’t know what it is exactly. That weapon is SSG, which Fujitora hyped to be so strong, they didn’t need the Shichibukai anymore to turn the balance against the Emperors.
With Mihawk facing the Marines at this point
And thus it could be a perfect way for Oda to test out Vegapunk’s SSG weapon, and the weapon’s properties as mentioned are unknown, but it’s possible that they could be composed of diamond material, and thus with Oda using that opportunity to test out Mihawk, and the pinnacle of swordsmanship challenge at the same time.
*Theory by Bogard