So this I less of a theory and more of a prediction. A little bit in it though is a theory.
So first thing is, I believe this is the last bounty increase we will get. And it will be the biggest yet.
Why is it the last? Well because after this arc we‘ll get the last Arc, which is against the world government. And after they are defeated, who is gonna put out bounties?
Monkey D. Luffy(1.5billion): I have to bounties that are possible for Luffy, 5billion ore 6Billion. Kaidos bounty(the highest active pirate bounty right now) is 4.6B, so Luffys should be higher. That’s why 5B is the minimum for me. It also fits with his bounty being round numbers. Why is 6B a possible? Roger had the highest bounty ever and he became pirate king, but he never actually defeated another yonkou. We know the yonkous of That time were Roger, WB, Big mom and shiki. He stole a copy of big moms PG but without taking her out, he drew Whitebeard in a fight and he never defeated shiki. Luffy on the other hand is actually take the yonkous on. And that’s the point were he surpasses even Roger. That’s why I think his bounty is gonna be higher than Rogers. So 6Billion it is.
Zorro(320Million): based on the last chapter Luffy told Law and Zorro to head down and he’ll fight kaido on his own. So it’s probably gonna be Zorro vs King. But Zorro has also shown other feats in this war. Like cutting kaido, something not many can do.
I think his bounty will be 2.4Billion.
Sanji(330Million): So Sanji is probably gonna defeat Queen and we know his bounty. Other than that we can’t actually predict his bounty. I’m thinking of something like 1.7B for Sanji.
Jinbe(438Million): again Jinbe is difficult, since he’s fighting Who‘s Who and we don’t know his bounty. But seing that Jinbe is fighting him he must be strong. This is also the fight where we will See Jinbe‘s Full strength and him going all out. A bounty of 800million is what I think.
Franky(94Million): currently is probably the 5 strongest in the strawhat crew. His opponent is Sasaki and his bounty is gonna skyrocket to something 650Million. I know what you guys are thinking it’s pretty high. But we’ve seen youkou crews have multiple members with 500M+ bounties. Big moms crew has 5 members with bounties oder that.
God Usopp(200Million): No bounty, just run for your life. I actually still don’t know if he’ll have a fight with page one or is it gonna change and he’ll have a role like in Enis Lobby. Either way his bounty is probably gonna double. 400million it is.
Chopper(100Berry): He is gonna put some real effort in this war. He has already shown his medical genius and he is gonna take out a lot of opponents. His bounty is gonna multiply buy 100x. 10K berry and rightly deserved that is
Robin(130Million): she is gonna kick Black Marias Ass. So she is showing the WG that not only can she read the PG she is also strong. So I’m guessing 350Million for her.
Brook(83Million): has managed to trick big mom on hole cake island, is gonna show us his incredible strength and when it comes to fighting probably the six strongest in the crew. Bounty 555Million
Nami(66Million): is gonna kick Ultis sorry Ass and gain an huge bounty increase. 260Milliom is my prediction here.
I think this Bounties are justified when you think about that, after this arc the strawhats have defeated a yonkou. Depending how they report it, they may make it look like the strawhats defeated 2 yonkous on there own. And they have 3 Road PG. the WG is gonna take actions.