I am guessing you are in a group that requires an instructor? I am sure this is driven by instructor availability.
I am guessing that some people drop out and/or instructors get added late so a last minute move (i.e just before two weeks or so) is possible depending on where you are placed on the wait list. I am guessing the likelihood of getting off the wait list is based on where you sit on the list.
I am sure the registrar knows — it would also be useful for participants to know so they can have some idea of the odds of going and can arrange their schedule accordingly. I don’t know if it is possible to keep that sort of information up to date or not (online tracking would be best but it may not be easily accomplished).