FYI, When I was on the waitlist two years ago I asked about what was the latest we would hear back and this is what I was told:
"I will be closing all remaining files after day one of class Aug. 28/17 as sometimes accepted applicants change their mind, go another route and leave us with an open spot which we would then scramble to fill at that time."
I got my rejection letter that year on Aug 28.
This year class starts on August 26th, so you won't know for quite a while if it is a rejection, but you could also get an acceptance that late if they have a spot to fill or if another waitlister rejects their spot. It's stressful, I know. Make your plans for next year and cross your fingers you get to cancel them!