I think Luffy will hit the 5.6 billions mark at the very end of the manga, but i find it very hard for SH to not get massive bounties after defeating two emperors (especially Zoro and Jinbe) even if not by themselves. But exactly as it was with WCI arc, i guess that the marines will think Luffy was the mastermind behind it all. And if after this Luffy really becomes a "New Emperor" i think it should be obvious for him to have at least two combatants above 1 billion. And after Wano the SH will have 3 Road Poneglyphs out of 4…there's no way the WG won't be worried about it, so i think Robin will get a significant increase too.
Luffy: 4.000.000.000
Jinbe: 1.230.000.000
Zoro: 1.060.000.000
Sanji: 770.000.000
Robin: 500.000.000
Usop: 350.000.000
Franky: 340.000.000
Brook: 333.000.000
Nami: 166.000.000
Chopper: 1.000.000