I think it's booze!
Specifically, I think it's Bink's Sake. It seems like Oda was really proud of making that song. He even wanted it studied in schools at one point. So I think it'll at least play a role in the ending.
Plus, we can even add "String Theory" to this! Joyboy gave Emeth the Giant Robot a Haki Knot, which seems like it's probably going to play a bigger role in the story in the future, somehow. And what are Sake Barrels in Japan traditionally held together with? That's right...KNOTS! Or bamboo or rice stalk straw ropes. So, it's possible that Bink's Sake has been sealed by Joyboy's Haki Knots to keep it aging until the right time, in the future.
https://www.sakedesu.com/sake-thoug...nce-of-barrels-of-sake-in-japanese-traditions
https://kokushu-museum.com/en/traditional-production/straw-rope-making/
But, lets add even another lair to this. Because I think it's possible that Bink's Sake could be Bink's himself! I think it's possible that Binks ate the Sake-Sake Fruit and became a Sake-man! So, he's been sitting around in a barrel "aging" himself to make himself more powerful this entire time. Think of it like a more goofy version of the practice of Sokushinbutsu, or a monk burying themselves also in order to achieve englightment in death. It means "Instant Ascension to Buddhahood". But, in this case it'd be more like "Sake-Shinbutsu", or "Ascending to Buddhahood...by using booze!" Basically, imagine a drunken-master version of the Kool-Aid Man, and you get the basic idea of how I imagine this guy.
https://en.wikipedia.org/wiki/Sokushinbutsu
Plus, if Bink's Sake IS Binks himself, then that means we can learn about the true history of the Void Century right from the mouth of someone who lived through it. Which, personally, I think would be more dramatic and dynamic than Robin reading the history off a wall or Poneglyph or something.
But why sake, you may ask? Well, I think it's basically going to be used as a peace offering to a group of people that Humanity has wronged in the past. A lot like with Luffy, Ace, and Sabo's sake drinking ceremony, I think Bink's Sake is going to be used to bring certain groups of people together. Which means, yes, they're going to have to drink this guy.
Because I think Luffy is going to end up freeing a group of people from what is, essentially, the Underworld. A group of people who were wrongfully imprisoned. As a parallel to Impel Down, in a way. And if Luffy DOES free this group of people, they're going to be rigthtfully angry at the whole of humanity to what has been done to them. So...Luffy's going to throw them a big "welcome home" party to try and de-escalate the situation. To bring Humanity and this other group back together again to share this world.
....And this group of people is likely actually Dragons.
Throughout this story, we've actually seen a lot of statues of Dragons. There are statues of Dragons in the bath houses of Alabasta. Fishman Island's Ryugu Palace has a giant Dragon statue on top of it. Wano has a Dragon statue that's in storage but was originally supposed to be at the entrance to the kingdom. Almost every country that seems to have been allied with Joyboy or Nika in the past has these Dragon statues somewhere. I wouldn't be surprised if we see a Dragon statue in Elbaf at some point too. And I don't think this is just decorations. I think this is foreshadowing. What if these statues aren't just there to look neat? What if they're around because these are actually statues of the previous world leaders of this planet? Like we would have statues of George Washington or King Charles in our major cities.
Because I think Humanity invaded the One Piece world and stole it from it's original inhabitants. I think humans originally came from space and invaded this world and conquered it for their home. Trapping the native inhabitants in a "reservation" where they're still alive today. We know from Enel's cover story that SOMETHING is going on with space. So, I think this is end up tying in, too.
And Dragons, in Japan, like booze. Just look at the story of Orochi and Susanoo. They would enjoy a party full of free alcohol.
Why was the Ancient Kingdom erased from history? Could they have actually have done it to themselves, like Vegapunk erased his own mind in order to make his plan work? Could the Ancient Kingdom have erased themselves from history, just to try to eliminate their racism and grudges towards the Dragon race? Or as a attempt to erase their sins against the Dragon race, because they felt guilty for stealing this world away from them?
And what is the reason the World Government tried to have Vegapunk clone Dragons and other possibly Dragon-adjacent races? Like the Dragon found on Punk Hazard and the Numbers on Wano? Even trying to capture Kaido alive over and over again? What better weapon to have against a army of Dragons, then other Dragons who can fight on your side?
So, yeah. I think One Piece ends with a thousand Dragons with the strength of Kaido all erupt from the Underworld at the center of the planet, ready for revenge. And Luffy will try to bring peace between the Dragons and Humanity by throwing a giant tailgate party.
If you want to read more, I have a whole 151 page PDF with more detail here:
https://worstgen.alwaysdata.net/for...message-will-be-the-dragons-are-coming.55673/
I lot of it has been deconfirmed just from the passage of time, but I still think the essence of the theory can still be intact.
As crazy as all this may sound, I do think it's a possibility. I'm probably completely off base. But, it was the best, most unique theory I could come up with, at the time.
