There will be lower attendance but not because the schools are limiting it. People are creatures of habit and for many, their lifestyle is now avoiding crowded areas. That doesn't go away in a couple of months. A year from now it will be much different in more ways than one. We will be in a global depression, and during those times people choose daily leisure activities like movies and football games over things like week long vacations and such. I wouldnt be surprised to see record attendance in 2021.fan revenue for the NFL is ~25% of their annual take, so I'm not sure that number is accurate more than it's owner posturing.
college football is much more beholden to fan support for revenue (upwards of 60-65% for G5 schools), to your point.
I absolutely expect fans in the stands, and would not be surprised to see full stadiums with no restrictions in many places.