I would be surprised if Rowling had anything to do with the actual unmasking. What would she gain. She already has fame and fortune.
Publishing under a pseudonym seems a bit "poor little rich girl who wants to be recognized for merit" to me, but having done that, why open herself to ridicule from the envious and cynical?
A lot of people are involved in her life and her publishing world, and I think that one or more of of them had something to gain by leaking the authors name, if only a fleeting moment of "I know something that you don't"