http://www.udel.edu/udaily/2015/may/board-of-trustees-051215.html
According to the article on UDaily, the freshman class will be approximately 200 students over target. This could be why they are not taking anyone off the waitlist.
I feel sorry for all of you not accepted off the waitlist since it’s taken so long, first to be put on the waitlist and then to be notified. Best of luck to all of you wherever you go.