As a result of the Revolutionary Army’s actions in Mary Geoise, Sabo has gained massive global influence and is now known as the “Flame Emperor”. Now, his influence is said to be even greater than Monkey D. Dragon’s himself.
Sabo’s introduction was always weird to me because I didn’t really see a reason for him to exist and why Oda would make him the 2nd in command of the Revolutionaries. Well I think with the latest chapter we finally know, Sabo will be the one to take on Im and the World Government.
From the beginning One Piece was never about fighting the Marines, they were just the villans of the week like pre timeskip Smoker or roadblocks like Aokiji and Kizaru. But beating them was never the goal of the series. I think Oda realized during Marineford that he had too many antagonists for the Straw Hats to beat and it would just take too long and be way too drawn out which is probably why he made Big Mom and Kaido team up so he could take them out of the story together.
So my crackpot theory is we’re going to have 2 arcs going on at the same time with Luffy going on the fulfill his destiny of being Joy Boy and whatever that entails. While Sabo and the Revolutionaries take on the Marines and the World Government. Most likely ending in a twin defeat of Blackbeard and Im at the same time by Luffy and Sabo respectively.