[Mark McLeod]

Ultimately, that comes down to how flexible teams are able to be.

Being on a waitlist doesn't get you into a particular competition.
Every year venues do fill up and waitlisted teams do get turned away.
Smoky Mountain had that very public problem last year and had to ask if two veteran teams would willing trade their slots to rookies in exchange for a different event. BAE, SBPLI, NYC, and others have to turn teams away each year. Most teams are able to switch events, especially in the high event density of the East and FiM/MAR. Some of them cannot. Room is made for everyone to play at least once though. That's what reserving some slots for waitlists helps guarantee.

FIRST will work with teams to find a substitute event, but the practicality of the event change depends on the team being able to take on any additional travel/food/housing expense, not having a conflict for an alternate weekend, school board approval for crossing state/country boarders, etc.