Situation for Notre Dame:
“Admissions received around 60 summer cancellations this year, in comparison to around 30 cancellations in past years. While this number was greater than in past years, Bishop said admissions prepared for an even greater loss. In addition, the number of students electing to take a gap year increased to around 60 to 100 students as opposed to the usual 15 to 20 students.”
Source: Notre Dame Observer
Harvard and MIT could “replace” the kids that deferred with kids from their waiting list but decided not to. And coming next year they can (if they wish) accept more transfers to go back to their numbers. I do not think they are “hit” with anything. Now other colleges that are not Harvard or MIT yes, that would be more of a problem.
For high school class of 2021 I think they could be more spring admit type programs to perhaps help colleges spread the kids than having a giant class start in the fall.