Kid and Law are guaranteed to go over a billion, have a relative high chance of being over Luffy's current 1.5 billion, but it would be an absolute travesty if they go over 2 billion.
I don't actually have much expectation for the two of them in Wano- at best, playing second and third place in defeating Kaido with Luffy waaaaay out front in first. I find the idea either of them would beat BM laughable- she's going to be on Elbaf, the two have next to nothing to do with her and Oda wouldn't even let Law beat his most hated rival, who was "only" a Warlord. To be quite honest I have more faith in BM contributing to Kaido's defeat than Kid and Law having a meaningful contributing to hers or Kaido's.
But Oda will continue to pay lip service to this idea he has planted that they are close enough to Luffy. And as far as I believe, lip service has all that's ever been, Luffy's totally outshone them every opportunity Oda get. Them standing side by side twice in ten years and beating fodder is meaningless to me because, when it comes down to the wire, Oda is always going to show Luffy in a vastly superior light.
But they are captains of the Worst Gen, the two most important captains out with Luffy and Blackbeard, and popular characters- Law more than Kid, which is fair, as Law actually has a personality and has contributed to the plot. So far Kid is just a Bellamy who believes in dreams. So Oda will give them a high bounty to keep up the bare-minimum rivalry.
But if they get near to the 2.2 billion that Blackbeard has, then what the fuck is Oda smoking? Blackbeard is an actual Yonko, with a crew that makes up at least four of the most horrible criminals the World Gov ever saw, the only man with two DF's, teamed up with a former Admiral killer of Whitebeard, destroyer of his crew, humiliated the World Gov at Marineford. Sure, his bounty is guaranteed to have a gargantuan rise soon enough- his current one really is far too low compared to the other Yonko- and bounties stopped making total sense a while ago, but that would be a step too far.