I have heard that Southwestern is really bad with their waitlist; they tend to string people along till classes start. I hope this is not your situation and they let you know soon. Maybe if you call and explain your dilemma they can give you some insight as to what they intend to do with the waitlist. I do not know if you will find out anything solid, but it might be worth a try in your situation.
Also, I was thinking of applying there in September, would you mind telling me your numbers?