Here is my thought on how the series might end. So, in Egghead, loads of stuff seem to be happening in parallel. Buggy basically convinced his crew to chase One Piece with Hawkeye and Crocodile. Law got his ass beat by Blackbeard and will likely get saved by someone. Kid’s status is unknown (my guess is he is not dead but will probably be shown to be alive towards the end of Egghead or will be found alive in Elbaf). Shanks is on his way to the final island. Blackbeard, I assume, will be on his way to the final island. Luffy’s crew, after they find the last Poneglyph, will be on their way to the final island.
There will be a fight against all of the mentioned crews at Laugh Tale. This is where we would see Zoro vs. Mihawk, Luffy vs. Blackbeard, Luffy + Kid + Law vs. Shanks, and maybe some other fights. The Straw Hats will be the first to “reach” One Piece but will open whatever message together with the others—such as Law, Kid, Shanks, Buggy, and the other pirates.
While that is happening, in parallel, the Revolutionaries are struggling with their fight against the Government/Imu/Marines. Sabo or someone from the Revolutionary side will reach out to Luffy, and the remnant pirates and their allies will join in the fight with the Revolutionaries to take down Imu and “free” the world. This would result in a crazy all-out war between the pirates and Revolutionaries vs. the Marines and Imu + Holy Knights and other allies. (I could see this happening, as we still need to see Luffy interact with the Revolutionaries before the series ends, and this would be a decent way.)
We’d probably see Kuzan flip sides, along with Garp, Smoker, Tashigi, and other Marines that Luffy has interacted with in a favorable manner. This is where we’d see Sabo and Marco vs. Akainu… etc.
Imagine it… a two-page manga panel of every major pirate we’ve seen in the series joining the fight and pulling up to take down Imu and his government/assist the Revolutionaries. If Oda gets every major character, it might be one of the greatest manga panels of all time.
