That's my point, there is no old theory, it's just same theory since ever
Idea of Zoro slaying a Dragon existed since ever, starting with Ryuma Parallel and then Kitetsu meaning Oni Slayer and then Dracule derived from word that means Dragon and then Mr. 1 having Dragon drawn on his clothes, not to mention Zoro Dragon attacks, his attempt to cut a Celestial Dragon, fighting Zombie Ryuma, slaying Punk Hazard Dragon, Kings last attack being in Dragon shape, Shiryu meaning Death Dragon, Zoro being given Tiger theme who is Anti-Dragon ... etc
His entire journey is about being Anti-Dragon. So a moment where Zoro slays a Real Dragon has always being anticipated since ever
It's just that people got excited when Wano Arc started since the villain is finally a Dragon God, and what was before just hints, became a huge theory that many Fans discuss
But just because Wano ended and I failed in predicting timing, doesn't mean I have to drop the idea of Zoro killing a Dragon which existed always, long before Kaidou got introduced even
And I guarantee u, this idea is based on conclusion made from research that includes all ten SHs, Its not that I want it so badly or anything, cuz Mihawk Fight is far more interesting to me if it happens
Cuz if we talk about wishful thoughts, I would have preferred it happened in Wano, now it doesn't have same impact, Kaidou won't look that intimidating compared to Final War roster of main villains and allied