Sounds like a great question for the program coordinator at Hopkins (not the PD, but rather the administrative person). No one here is likely to have any real idea. Imagine the odds of finding even one random board-poster who had been wait-listed there, and even still, they'd have no idea what the denominator is.
Perhaps a better question would be why on earth they have a waitlist for interviews. What do they think you'll do, turn down other interview offers, knowing that you're on the list at Hopkins and you're just holding out for that chance to interview with them? I don't see how a waitlist for an interview helps anybody.
