The notion of a “cliff” might evoke a somewhat more dramatic vision than is warranted, but here is one projection (this is of total US HS graduates per year):
That is projecting right around a 1% average decline per year.
A couple things to keep in mind. This is just the domestic population, and at least some US colleges have been experiencing significant increases in international applications. And then applications per applicant have increased as well.
For a broad overview, Common App does regular updates (obviously this is only Common App data, but I am not aware of a reason to think it is not at least reasonably representative):
Here is the latest one from March:
In the “at a glance” section at the top, you can see how, among other things, International applicant growth has significantly outpaced domestic (13% to 5% during this study period).
In the “key findings” section, they then report:
Total application volume to returning members through March 1 rose 7% from 2022–23 (7,041,256) to 2023–24 (7,541,148). Applicants were also applying to slightly more members in 2023–24 than in 2022–23 (+1% from 5.66 to 5.74 applications per applicant).
I note they also report 6% growth in unique applicants, which means the 13% International growth was enough to raise the total by about 1% (since it was only 5% domestic).
Long story short, I am not sure a “cliff” which amounts to a 1% national decline a year in the domestic supply of high school graduates is going to reverse, or even do much to slow down, the upward trend in application volumes at the more popular national/international colleges.
Indeed, just very back of the envelope–the underlying “cliff” is basically going from around a 1% annual increase to a 1% annual decrease, so a net of -2%. But if the baseline trend with all the other factors included is something like a 7% annual increase, then that may only slow down to like a 5% annual increase.
But we shall see.
That FB page will be your source of info!