I am guessing that the first round of waitlist letters went out, since at least one person got one in early May, and I think I read above somewhere that one's response to a successful PDF had to be in by the end of April. But maybe there will be a second round of waitlist offers...although the chances of that are pretty slim I think.
I don't think anyone is really reading this anymore, but to those who are still doing their PhD programs. If you're concerned about the PDF numbers this year (there's no reason to think they'll go back up and it'll affect you sooner than you think!), you should really write or talk to, and get your fellow students to write or cosign, letters to your department chair, someone higher up in your uni, or even the local MP. Nobody except us really cares about this, so it's up to the grad student community to change it.