I believe they keep it open until then because there may be cancellations but when I talked to admissions a few weeks ago, they said the class is "overfilled" and they probably wouldn't be taking anyone off of the wait list even if there were cancellations. Also, they said really the wait list is only open until July because there are certain procedures that students need to do that would need to be started by then in order to be cleared to start school in the fall, I'm guessing background checks or something? Not sure. :-/