I think Kidd and law are done till the last war. Their bounties probably stay the same till eos. There's nothing they can really do to increase their bounties. They aren't soloing a yonko, they aren't doing anything massive anymore as that's going to shanks Luffy and BB, and they are currently defeated while the story is racing towards crowning the pk. The most law might do is expose some of the real history of the world which let's just give him another 500 million to 1 billion increase for that but Kidd has nothing he can do to increase. Imo zoro's last bounty will probably fall between 3.5 to 4 billion. Be will be the #2 of the pk, the Wss by beating mihawk, and may take out a admiral or gorosei as his last feats which would make him huge threat to the WG.