There are a lot of promotions are working together right now. Former WWE star Matt Hardy recently talked on this matter. His current promotion the All Elite Wrestling is working with the Impact Wrestling and other promotions as well.
One of the biggest prospects in the world of professional wrestling right now Kenny Omega is carrying three different championships from three different promotions. One of them is the AEW World Championship, one is the Impact Wrestling World Heavyweight Championship, and the other one is Lucha Libre AAA Mega Championship.

Matt Hardy On Promotions Working Together
Such incidents were common in the Independence Circuits, but mainstream promotions do not allow their wrestlers to do such things. But with Omega receiving such a treatment, it could be said that outside of WWE anything is possible.
Speaking of the WWE, they are only promotion that do not allow their wrestlers to work elsewhere. But things did not remain the same earlier. There were a time when WWE allowed wrestlers from other promotions to work in WWE. But with time they became the best in the world, and they stopped it.

Former ECW World Champion Matt Hardy recently talked on this matter when he spoke to ET Canada. He said;
“I think it’s great. I’ve always thought it was great for business. A Lot of people don’t know about this. It’s not a well-known fact. But I had been negotiating and working with the Young Bucks. And right before my brother and I left Impact to return to WWE, we were actually going to do a Ring of Honor-Impact crossover angle with the Hardys and the Young Bucks for three or four months. And we had that set.
“But then some things changed in their management and then ended up we’d return to would return to WWE once we ended up leaving. So I’m all down for it. I’ve always been down from it from the beginning. And I think especially considering WWE is such a massive global promotion, I think any other promotion that is up-and-coming when they work with other promotions, has it helps to add the element of unpredictability and unpredictability is what makes wrestling successful in 2021.

“I think more than anything else, because information’s out there, so many people see spoilers, so many people have a clue of what’s going on because the Internet is very wide and people know. So I think the more you can surprise people, you have someone show up on this promotion or someone show up on AEW or someone shows up in New Japan, I think it really adds that unpredictability to pro wrestling.”