Luffy will get 3 Billions. Oda usually gives round lvl bounties to Luffy, will come out of the arc with his subordinates being capable to defeat the main core members of yonko crews(veteran, yonko commanders), with the Strawhat grandfleet already known to the world, the hype behind potential 5th yonko coming to conclusion and there should be a Luffy vs Kaido chapter, where Luffy will ultimately break his 1 on 1 hype(although against a weakened Kaido), a feat that should be viewed as superior to Blackbeard's feat in overwhelming Marco's group, so based on that, i think Luffy's bounty should hit 3 Billions after this arc.
It's also not a problem for Luffy to surpass current Blackbeard's bounty since Oda already has Blackbeard on the move, which makes me think that he'd do something that will increase his bounty as well, probably with Blackbeard ending up portrayed as the ultimate threat after Kaido's defeat as a way to still portray Luffy as the underdog