BB will get what the marines are after and add to his forces(probably Pluton).
Shanks is the strongest emperor and most likely Mihawk will join him after the end of the Shichibukai.
Luffy is becoming as strong as a emperor and will get all Samurai and Mink forces under him after Wano, and some big allies like Marco.
BM and Kaido will fall, but the other three will fill the gap.
And theres other Pirates like Law, Kid, Buggy, Weevil, Caponne, Katakuri and the BM pirates remenants, Apoo and the Numbers and pehaps even Jack and Beast Pirates remenants, that can make this second tier pirates that the Warlords were part.
But of course the WG will keep being the strongest organization, they are the final villain and while Shanks and BB will fall, Luffy umbrella will grow to be able to clash with the WG power.