Western sends out waitlist offers every 24 hours, depending on acceptances vs rejections. They send out an offer, wait 24 hours to hear back, and then depending on the response, continue to move down the list. In theory, people could back out of their spot or hear from another school elsewhere up until classes start, so it is difficult to say whether or not you will hear back. But I can't imagine any schools send all their waitlist offers out in one day, as they could receive too many or too few acceptances and then be in a tough situation.