Klitschko-Haye was bigger fight but it turned out to be flop. I remember it was more hyped, that fight was talked over 2 years before it was made.
And don't forget he has to choose. Both mandatories are due, and he can't fight both of them at the same night. Which means either Usyk, Pulev or neither. He will lose one belt at least for sure, and like you mentioned, the PBC doesn't even recognize the WBO one, so that one is almost a certainty to be vacated. My money is on either Usyk vs ex beltholder Parker for the vacant belt, or it might even be up in Usyk's next fight with Chisora (the WBO has done way worse with vacant belts). If Joshua wins however I don't know who he'll choose to fight. much more hyped and a much bigger fight for sure.
I do believe Joshua´s side could work things out with the mandatories. Ruiz might even give up the IBF belt as well, who knows? What we do know is that Pulev is 100% going after it. It´s all a big mess.
It has always been a mess. Everytime a unified beltholder gets beaten there's a huge chance the belts get scattered all over the place again.
Wow! Finally 2 of the alphabets acting the way they should. This might be a sign of the apocalypse though. Warn me when it starts raining blood, the dead rise and we get locust plague's all around.