According to last year's thread, rejections came out on April 12, and winners had to accept by April 13. My guess is they're just waiting for all the winners to accept before sending out the final wave of rejections, and all winners accepted a little early.
Since Grey28's husband has to respond by April 26, and given last year's similar timeline, I suspect we'll hear towards the end of the week. Let's see what happens!
Another interesting fact from last year's thread is that two versions of the rejection email went out. One version included the line "We were very impressed with your credentials and saw much promise in your application and we strongly encourage you to reapply next year provided you remain eligible." This was assumed to be some sort of unofficial honorable mention by the posters. There was no mention of any waitlist, but my guess is if there were, these "honorable mention" winners would have been on it.