Think Luffy final bounty will be 5.6b, making the joke Go-Mu(5-6), and becoming the biggest pirate bounty ever, over Roger. But he probably will get this bounty only after Laftel, and the Wano increase will not be his final one, so i believe he will get something around 3b now, for his bounty to become huge, but still lower than Teach bounty(5b), for Luffy to be the underdog in his fight against the BBP.
The defeat of BM and Kaido will not bee work of Luffy, Kid and Law alone, and probably the WG will be involved in taking one if them, soo i dont think the Supernovas bounties will go over the Emperors ones by now.
If Luffy go to 5b now, them get a increase of 600m for finding the OP dont make Sense.