If it's open then the admin simply hasn't reviewed it yet. I mentioned it in a similar topic here, but the last time GameFAQs offered a username change as a t-shirt bonus it took quite a while for everyone to get their name changed, a few users had to wait a few weeks iirc. We can't give you a more accurate timetable or provide an explanation as to why since only SBAllen handles that stuff, but just be patient and he'll get to it eventually. =p
All good things must come to an end - preferably in a humongous explosion!