You can even do this when you don’t know the exact interval by using probabilities. The Allies used this method to estimate German tank production in World War II by analyzing the serial numbers of captured or destroyed tanks.
This is know as the German Tank Problem [1]
I’m a lawyer and using sequential IDs in a fraud case right now, to determine the number of victims.
Unfortunately, so far, I only have the IDs of two victims, and those are from just within about a month, whereas the fraud has likely been going on for several years. Just simply extrapolating that growth rate isn’t going to be very accurate.
Also, I suspect that the perpetrators did not start at ID 1.
that'll be like trying to determine the average salary in a company with only two known ones, which could be the janitor's and the CEO's
Ironically that would be somewhat close to the actual average.
If you have integer IDs it is also trivial to find authorization flaws on your own. Any pentester will go for it right away.
If you make non guessable IDs they might skip it and go look for other stuff.