I don't understand why kidd or law should have bounties of 2b+... why??? They are not luffys rivals, they are FROM THE SAME GENERATION. His only rival is blackbeard, which was build up since jaya, while blackbeard was mentioned even before in drum.
The supernova are late to the story and oda himself said that he added them so that the arc won't be too lame.
I am not saying that they are not important, nope, just that they will "bow down" before luffy except blackbeard. Just like law did, which is PERFECTLY FINE (for example he said to luffy: "you are the worst (of the worst generation)).
So I believe that they won't have a bounty higher than 1+ after wano, later, yes. But not after wano.
Because they won't be considered a yonko after wano, like lufyy after wci, because they lack the power, crew, fleet, allies, countries, threat. All of them. FOR NOW (after wano).