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).
This may be one of those intractable problems.