Let's set the stage.
- Strawhat Luffy alongside Kidd and Law took down two of the yonko
- The revolutionaries have struct at the heart of the World Government and Several Nations have revolted under the inspiration of the Flame Emperor
- The World Government recently unleashed their replacement for the Warlord system, the Seraphim
- Due to Morgan's propoganda, the world at large will believe that the Strawhat pirates kidnapped the world's most brilliant scientist
- 100 naval ships are descending upon Egghead island under the command of a member of the strongest force of the World Government (Admiral Kizaru)
- A member of the Gorosei is in attendance
All of these pieces are currently in place either before or during Egghead
As the story progresses it seems inevitable that the strawhat pirates will clash with Kizaru on Egghead. Under the presumption that they do not just slip away and actually face him down there(And presumably Saturn taking part) I think it's safe to say that a victory would be the most world shattering event in One Piece.
This is because this would mark the Yonkou strawhat luffy as having
- Kidnapped (or killed depending on how the interaction goes) Vegapunk
- Destroyed a Marine fleet larger than the one at the War of the Best
- Taken down one of the Admirals
- Capture/Defeat the Seraphim
- Capture/Defeat one of the Gorosei
In essence, they would have made the Marines bleed like no other opponent has, completely end the replacement for one of the three great powers, remove the source of the World Government's technological advantage and manage to touch one of the Rulers of the World Government.
All at the same time.
This would be absolutely world upending. In one battle, the strawhats could potentially do more damage to the World Government than arguably every single pirate (and revolutionary) since the Dawn of the age of Piracy COMBINED.