I think it would be a good idea. I was from one of the forums that shut down, and it sucks. Anyways, it can take less risk of other forums closing, and it can unify fans. Those who wanna join can just see 1 BIG happy community than a lot...
I was also a poster in a wrestling forums, and it got unified to another big forums, yes its more work for it means more members and lots of moderating to do, but in the end its worth it. It will be more lively. And we can really get opinions and great discussions from lots of fans.
And how to get them together? In the unification of the WWE forums, whichever community one belonged to, they just have to log in to their original names and passwords, and they can get in to the unified site.