And, when next season is cancelled, then what? Ask for more donations? You assume things will be normal next fall. Let me give you a clue, the economy is shut down. We have not yet peaked in cases. We can only guess that cases will reduce. I have seen estimates that some peaks will not occur until August. That is well into fall practice. At best, we might see a reduced season.
As for the average fan, I think they will be paying off bills, helping others pay off bills, and volunteering to feed the souls who are still jobless with anything they can scrape together. If Covid-19 continues in any scale other than zero cases, there will be no large gatherings on the scale of a full football stadium.
There is still no study that suggest we will have immunity from SARS-CoV-2 or if the other 7 strains can get you sick again or what those strains disease state looks like.
You appear more optimistic. That's okay. I hold a view that this is going to take several months or even years to get over, if ever as far as the impact on society. We shall see.
The risk isn't on the interest, it is on the principal. If there are no students on campus, and campus activities remain cancelled, then say goodbye to the athletic department. Giving them a loan would be pointless, billion dollar endowment or not. And, I would venture to say that endowment is not worth what it was a month ago. In which case, the stewardship of that endowment will become more stringent, not less.