I'm really not sure what the point is in scheduling a spring football season, other than futilely attempting to quell some of the revolt resulting from cancelling the fall season. What is going to change between now and late February, when they'd have to be practicing?
1) COVID won't get less dangerous.
2) COVID won't get less transmissible.
3) Relative to cold/flu season we'll be in the same calendar territory we were when the 2020 NCAAT had to be cancelled.
4) A vaccine may exist but the American population is very unlikely to have received it at scale that early.
5) Football isn't going to be less face-to-face than it is now.
6) 20yo athletes aren't going to be more responsible about transmission/more able to limit transmission in March than they are now.
In spring, people said it would somehow go away in summer because it would be hot. Instead, Americans are dying from it at a clip of about a thousand per day. And as Jim Sumner pointed out in this thread a while ago, it's actually a scarier situation if the heat/humidity has in fact helped. If that's the case, what does October-March flu season look like? A large percentage of the population refuses to take even basic precautions to limit spread.
For purposes of playing football, nothing's going to be different, except the death toll will be much higher by then and the average person will be closer to vaccination day than they are now. If you listen to actual epidemiology professionals, we will not be anywhere close to herd immunity, neither by relatively unchecked transmission nor by mass vaccination.
Absent some magical thinking about vaccine efficacy and delivery, I cannot think of a single reason spring 2021 football will be more feasible than Fall 2020 football.