Waitlist activity can vary widely from year to year at a given school, but many schools are getting much better at predicting their yields which has decreased waitlist admissions. Further, most schools are need aware when going to the waitlist, and with financial aid budgets typically fully spent by that time, full pay waitlist apps have an advantage.
Whether you accept the waitlist spots or not, make sure to put down a deposit at a school that accepted you by May 1. You may lose that deposit if you do get off the waitlist and choose to accept. Good luck.