I interviewed at SLU on 3/21; before I went, I called the office and asked if they were interviewing for actual spots or waitlist-spots. They said they were still trying to fill the actual class seats, and would be throughout the spring.
Obviously, I can't verify this, as I'm pretty sure the offices of schools routinely lie to applicants about things like this. Pretty crappy to do to someone who was spending lots of $$$ on plane ticket, hotel, car rental, etc, etc.
We'll see. Best of luck to you.