I was notified of a waitlist very close to 4/15 this year. I responded by thanking them, reiterating my strong interest, and asking if they had any idea of if/when they might send out more offers. They said they didn't know.
I would think that most of the movement would have occurred on the first day or two after 4/15, but I'm being optimistic. Historically speaking, do I have any chance, or is it an implicit reject at this point?