The "queerness" of Who's Afraid of Virginia Woolf, as far as I know, has always just been the wishful thinking of others, and Albee himself (if I remember correctly) refuted any ideas that George and Martha are stand-ins for a gay male couple. It was a tad unusual to have queer actors cast as both George and Nick, but both are (were) good fits for the parts and I imagine it was mostly a coincidence. I will say from experience though that many gay male directors do seem to prefer to work with other gay men - show business, like every other business, is built on relationships, and people generally prefer to surround themselves with people they identify with. Someone should do a statistical study, but it seems that in most businesses, theatre-related or not, the people who do the hiring tend to lean towards hiring someone of their "group," especially if it is a minority group.
That said, I doubt Rupert Everett was cast because he is gay. They just needed a famous film actor that was willing to sacrifice TV/film money to do a play on Broadway, and that was appropriate for the part. Rupert Everett seems like a good choice for George and will do fine I'm sure. Besides, if the Albee estate goes nuts whenever a theatre company tries to do a POC Virginia Woolf, I seriously doubt they will allow queer-themed Virginia Woolf. How would you do that anyway without changing the script?