Anybody with interent access can edit pages on Wikipedia. Unless a guest is announced on either this forum, the LFCC website, or the relevant Twitter/Facebook pages then it is best to ignore it.
Edit: David beat me to it, but I used more words
I know anyone can edit it, but still it would be amazing if it turned out to be true! I am not holding out for it to happen as there was a Glee convention last year (sadly I couldn't afford to go) and the guests ended up changing with barely couple of weeks to go! So I know even if it is true, they could still pull out.