In Chapter 1052, Apoo appears in front of Kid and Law who are discussing the newly established alliance relationship. Apoo said that information regarding what happened during the battle at Onigashima and everything else was leaked outside of Wano.
However, they were still wondering who had leaked all the information regarding the events in Onigashima and Wano. The leaks about the events in Wano apparently affected their bounty. In the newspaper that Apoo brought, he said that the bounty of Trafalgar Law and Eustass Kid had increased drastically.
In addition, the newspaper also mentioned that there were already names that would become the new Yonko figures to replace Kaido and Big Mom. Unfortunately, the chapter does not reveal the name of the new Yonko. But I am pretty sure that only Kid and Law are going to be considered Yonko.
We learn early on that Yonko’s are “even”. Their fights usually always end in stalemate. As such, when Luffy fought Big Mom evenly (Taking out Katakuri, and escaping from Big Mom unharmed), Big News gave Luffy the title “5th Emperor”.
We see Kaido and Big Mom fight for a period during Wano with neither side “winning”. Same goes for Shanks vs Whitebeard, Roger vs Whitebeard, Shanks vs Kaido, as well as Shanks vs Blackbeard.
However, occasionally an alliance will form to take down an “Emperor”. We see World Government and Blackbeard work together to bring down the Yonko Whitebeard. We see Big Mom and Kaido team up to “try” and bring down Luffy. We see Kid and Law work together to bring down Big Mom.
When Kid and Law worked together to bring down Big Mom, they did so with the power level of a Yonko.
However, There has now been a definitive “Winner” in a 1v1 fight of an Emperor for the first time in the series. Luffy is “stronger” than a Yonko. He didn’t fight to stalemate. He fought to victory, to currently stand on top of the pirate world, alone.
Yes Luffy had the alliance, but that’s not exactly how Big News Morgan will portray it. First and foremost he is a news Tycoon. Announcing the “New Yonkos” is to distract us from the New Title that will be announced with the latest Edition. Much like how Ryuma gained the status of Sword God when he defeated the Wano Dragon (without his knowledge or agreement), I think Luffy will prematurely be crowned King as he stands above Yonko now.
Theory by ErisGrey (https://www.reddit.com/user/ErisGrey)