First, let’s go back to the basics. The World Government comprising of 170+ countries is the One Piece world’s only government and political party. It is lead by the Five Elders and was formed over 800 years back.
Now let’s get to my theory…. The marines led by Fleet Admiral Sakazuki will perform a coup and overthrow the current world government leaders.
Abolition Of The Shichibukai System
As read in One Piece Chapter 735, Admiral Fujitora wishes to “abolish” the Shichibukai System.
The Marines have shown to have a general hatred for Pirates, and it’s obvious. Both these factions are always at war, lives are lost on both sides. The Marines oppose the Pirates at every given opportunity. This general hate for Pirates doesn’t die down. As shown first by Smoker, even though Crocodile was a Shichibukai, Smoker hated him and didn’t trust him. This hatred for Shichibukai has been shown by many other Marines, including: Ex-Fleet Admiral Sengoku, Ex-Vice Admiral Garp, Ex-Admiral Akainu and Admiral Kizaru.
The Marines play no role in the selection process of Pirates who become Shichibukai. The pact is made between a Pirate and the Five Elders. Often, the Marines end up suffering and paying the price for rouge Shichibukai such as Crocodile and Blackbeard.
How in our world, soldiers stand by other soldiers, Marines also have respect and consideration for one another. To see someone who has caused pain, misery and suffering to a fellow Marine be appointed as a Shichibukai, it would upset any Marine.
The Five Elders also consider the “Shichibukai” to be one of the Three Great Powers, along with Yonko and Marines. If the Marines decide to put an end to the Shichibukai system, that means they are directly going against the Five Elders and the World Government.
Fleet Admiral Sakazuki
Fleet Admiral Sakazuki also made the Marines much stronger as noted by Jinbei even though the Marines lost great and powerful members. This shows that the Marines have grown much stronger and gained many new powerful members through the Global Military Enlistment.
Fleet Admiral Sakazuki is also a strategical mastermind as shown in the Whitebeard War.
The Five Elders
Overthrowing Of The World Government and Introduction Of Revolutionaries As The Third Power
The Marines led by Sakazuki will overthrow the current leaders of the World Government, Sakazuki either himself will lead the New World Government, or will place a panel of his choice to lead the new government.
Along with the abolition of the Shichibukai and the coup that will overthrow the Five Elders, two powers of the previous three will remain, the first being Marines and the second being Yonko’s, once this happens a third power will emerge and take it’s place, the Revolutionaries.
*Theory by Divvens