After Dressrosa arc most of the crew’s bounties were raised by 50 million. Only the main problem makers got an enormous raise in their bounties.
Luffy is currently at Whole Cake Island, and there, he has completely destroyed Big Mom’s plan for obtaining the military strength of Germa 66. Luffy & co. will probably get a bounty increase for their actions against Big Mom.
Assuming that 100,000,000 will be the default increase for the events since they’re dealing with a Yonko (in this case Zoro could reach 420,000,000, Franky 190,000,000, Nico Robin 230,000,000, Usopp 300,000,000), here’s my estimates:
Luffy should have the biggest boost for being one of the mastermind of the commotion at Whole Cake Island, stealing Jinbe from Big Mom, working with the Fire Tank Pirates, working with the Germa 66, defeating one of the Three Sweet Commanders Charlotte Cracker, maybe defeating the strongest Sweet Commander Charlotte Katakuri. His bounty could reach 750,000,000!!
Sanji also should have a big boost for being the son of Judge Vinsmoke, which will now be public knowledge, for escaping under Germa Kingdom’s custody, for revolting against Big Mom and for taking her daughter. Now he is making the cake for Big Mom with a secret ingredient. His bounty could reach 350,000,000.