Blackbeard is also making his move, nothing suggests he won`t have an insane increase as well. And yeah Blackbeard could be closer which is why he will still have a bigger bounty (also because the guy is hunting DF`s like a sport) than Luffy after Wano and as you said bounties aren`t only strenght related, Luffy and BB will be the two biggest threats to the WG even bigger than Roger and Whitebeard (who chose not to find the OP) and again I see no reason as to why Kaido or Big Mom would have a bigger bounty than Luffy and BB after Wano.
Luffys only been the pirate for two years. His name recognition is crap compared to the others. And Kaidos gone through a freaking gauntlet, Luffy beating Kaido doesn’t mean he’s stronger than Kaido. Kaidos been canonically weakened
Blackbeard’s bounty I think will be 5.096 billion when we fight him, a bit above Whitebeards, and 96 = Kuro or black.
Luffy at most will have like 4.056 billion. Just barely above shanks. with the 56 = Gomu. And this is if we don’t fight shanks.
I’m still thinking it’ll be in the 3 billions.