I think this is going to be second (or third) last bounty of the crew. So Eiichiro Oda has to be careful.
As we know after this battle there will be a enormous battle. This is probably WG vs Straw Hat.
So after defeating WG there wont be any bounty :D
After Wano battle they will get bounty
The fight after Blackbeard they will get bounty
After reaching Raftel they will get another bounty (LAST BOUNTY.)
Somehow World Government knew that Roger had reached Raftel
In this page you can easily see that...How they can say ''Birth of the Pirate King'' without knowing Roger is in Raftel or not.Same will happen to Luffy and his crew.
So i dont think he will reach like 4.5-4.7 billion. That is going to be too early for him.
Luffy has to be at least 3 million. He will destroy one of the yonkos and this yonkou has 4.6 billion bounty. This arc he will gain his 3th road poneglyph (WCI-ZOU-AND WANO). As we know CP0 is in Wano so they will be aware who is going to take it.
Zoro definetly will have a higher bounty then Sanji. Not because of his achivement against Kaido , he will have it bc of title of supernova i think.
The whole world can know this battle like supernovas vs Kaido Big Mom.
So Zoro would have like 2 billion or 1.8 billion bounty. He wont reach 3 billion level.
Sanji will have around 1.3 billion.
And in this arc i think the joke about Chopper will end as a only zoan user in Straw Hat crew. He will use his power in battle and CP0 definitely see it. Or maybe they might have interaction with Chopper because we know Cp0 wants pirates to destroy eachselves. Antidot is a barrier to this.