Many people don't have any acceptances yet and are wondering how likely they are to get accepted off at least one waitlist. Hopefully, this will give a rough idea.

worldmetrics org states that the "national average waitlist acceptance rate is 21%." Although it doesn't provide a source is therefore untrustworthy, it gives a baseline for calculating your chance of getting off at least one waitlist.

Example for someone on 6 waitlists: You have a 100-21%=79% chance of getting rejected by a school. The chance of you getting rejected by all 6 schools is (0.79)^6=24%. The chance of you not getting rejected by all 6 schools is 100-24%=76%. Ie, you'd have a 76% chance of getting off at least one waitlist.

Yes, the 21% chance (and my graph that's based on it) is an overgeneralization. For example, lower-tier schools have more WL movement than higher-tier schools. You can view this document for more details.