I remember Rock Hudson -- all those years having to hide his homosexuality...even to the point of marrying for a brief period. In his day, being gay would have killed his career for sure. Toward the end of his life, when it was finally revealed for sure, Hollywood and most of his fans rallied to him. Wouldn't have happened years ago.
It may not end his career, but I think it'd probably weaken his box office power. It'd kill a lot of wistful fantasies, and that has to have a commercial impact.