As far as I know, there’s no indexing of the $500,000/student threshold for the endowment tax.
I’m curious to see what happens to this tax going forward. The cutoff might be lowered. The cutoff might be raised. “Students” might be defined differently. The tax might be eliminated altogether. The tax might be imposed on the total value of the endowment. Universities that meet certain goals (e.g. admitting a certain percentage of low income students) might be exempt. And so on.