As indicated in a sticky above, USNA's wait list is for those very, very close to a direct appointment. In some years, quite a few (maybe 50) WL candidates were offered appointments. In other years, none/almost none were. Last year was particularly tough and few, if any WL candidates received appts.
WL notices usually come at the same time as "rejection" letters. USNA tries to let WL candidates know their final status in May but, as the above posters have said, it can drag out well into June -- which, in my personal view, is unfortunate.
If you are WL'ed, you MUST pursue Plan B. Don't count on an appointment. If it comes, then you have a decision to make, But, as noted, you can't count on it. I will say that, if you're WL'ed, you have a good shot if you reapply, if you choose to do so.