No four emperors anymore, the story is entering the endgame, there wont be the same world system after the finding of One Piece and the Final War.
The chaos from the fall of Kaido and BM will be even bigger than WB one, as Teach already knew WB territores he was able to take a lot of it faster than a new pirate would be able to do and BM and Kaido being two veterans with established forces probaly also have taken some key territories, but with the two out, there will be no veteran to fill the void in power they will left. And this chaos will be what will lead to the final war.
The power structure of post Wano i think will be something like:
-Shanks, Teach and Luffy as the one with fame, territoriess, feats and manpower to be seen as the three Great Pirates;
-The Navy starting a heavy expantion on the NW;
-Smaller pirates, Supernovas and remenants of the Emperos crews taking territories for themselfs, like Katakuri taking WCI;
-Kid, Law and Buggy being seen as contenders to be the fourth Great Pirate. Kid and Law for defeating BM, but lacking manpower, territories and infamy, while Buggy, even if he is a gag, has all those things and probably will get a huge bounty after the end of the Warlords system.