At least you don't get rejected outright
It depends on their yield rate (how many people will accept the offer). Just keep track of the Tracker and see how many people with admit will select Yes in the Will Join column.
In years past, they even have to offer scholarship for people to defer enrollment until next year because the program is oversubscribed. It's not clear they will have same problem this year. https://www.quantnet.com/threads/oversubscribed-mit-mfin-offers-admitted-students-8k-to-defer.6320/
And now, for the most ridiculous question from the online waitlist chat for your entertainment:
I wonder if it is possible that an admitted student who personally want to give up a place recommend some waitlisted applicant. Will you re-consider the recommended applicant's profile and chance of admission under this circumstance? Thanks!!