We all know that the World Government issues bounties so my prediction is going to be on what the World Government sees as the most threat to their organisation.
Threat can be classified here in two types, active and passive:
Active being the ones who are actively opposing the World Government i.e. The Revolutionary Army so it’s obvious that Monkey D. Dragon has the highest bounty among the characters which are alive (around 10,000,000,000 Berries I guess).
Passive threat means the ones who may in future create a huge problem to the WG establishment for example if someone found One Piece it would “turn the World upside down”.
So the person who has the highest probability of getting One Piece is sure to be the biggest potential danger to the World Government.
The Yonko due to their power level are now the best contenders as they are not only powerful but also have big powerful connections.
Shanks was a member of the Roger Pirates Crew and he may know or may not know the location of Raftel but what matters is how the World Government perceives him and they see him as the former crew mate of the Roger Pirates. This information is enough to make them terrified of him.
Look at Buggy. He is the weakest among all the Shichibukai and we, as readers, may think that he fooled the World Government in thinking that he was strong but that’s not the case. The very fact he was also the crewmate of Gol D. Roger was worrisome, so the World Government tried to make him their ally by bestowing him the title of Shichibukai.
Not to mention that Shanks is very calm and far sighted. That’s how he was able to arrive just in time to end the Marineford War and also knew deep down the fate of Ace so he warned Whitebeard about it. All this makes him rather a threat to the World Government.
Marshall D. Teach is shrewd and cunning along with one of the most powerful pirate crews that have been shown so far. Not to mention Aokiji, a former Admiral, that affiliated himself with the Blackbeard Pirates.
Teach too possesses the most threat to the World Government as he too may know a lot about Marines because of Aokiji. He also has the 2 most powerful devil fruits in the series. So all these factors make him number two in terms of bounty.
Big Mom and Kaido each possess a Road Poneglyph.
Kaido is known as “Strongest Creature in the World.” He is mostly known for his ability to survive death.
He has created an army of over 500 Artificial Zoan-type Devil Fruit users and he surely would have made quite a lot up till now whereas Big Mom’s big plan was to create an army of Giants and she failed twice, once during Lola’s wedding and second when she wanted Caesar to create an army which he failed. Her next step was to acquire the technology of Germa 66 but this plan was ruined by Luffy. So all these factors make Charlotte Linlin the Yonko with the lowest bounty.
Now I will speculate on the current Yonko’s Bounties:
Big Mom would be around 3,500,000,000 Berries.
Kaido would be around 4,500,000,000 Berries.
Blackbeard would around 5,000,000,000 Berries.
Shanks would be around 7,500,000,000 Berries.
*Theory by bluebus32