Waitlists can often remain active throughout the summer depending on the school. Each school has its own unique process, but their goals are the same: fill the incoming class.
If you want to move off a waitlist, send a letter to the admissions committee indicating your intent to enroll if accepted off the waitlist. Letters of intent are essential because they tell schools that if they give you an offer, it will be accepted.
If you are not ready to commit to a singular school, then you can also reach out to their admissions office and ask them for a general timeline.