I'll post up what I remember them saying when I was there just a few weeks ago for my interview...the waitlist will be made at the beginning of June. They are actively accepting people from the under consideration category at the moment, to try and create a full class. They wait until June to create a waitlist because they want to offer acceptances to people in the under consideration category when the masses withdraw right at May 15.
Mrs. Nanos said that they have greatly altered the number of outright acceptances they offered this year, as they want to be able to utilize their waitlist. They will pull people from the UC category after May 15 til sometime in June, when an official waitlist will be created. They plan on drastically cutting the UC category down to create the waitlist, so there is really maybe only another month of having no idea where you stand on the UC category. Then we will either have been accepted (to fill in after May 15), placed on the waitlist (meaning we were somewhere in the middle of the UC pack), or rejected from UC and not placed on an official waitlist (at the bottom of the pack with no real shot anyways). Good luck guys, just a couple weeks left in the land of not knowing!