Football already does lose athletes to other sports because

of the factors you mention. It may accelerate, but I don't see it having any sort of significant effect on the game. I think the bigger issue is that due to CTE and the perceived toxic masculinity of the sport, a lot of parents don't want to let their kids play football anymore, particularly in middle class and affluent parts of blue America. Because of that, I can see football beginning to skew even poorer and more southeastern than it already does. I think it could end up being somewhat similar to hockey, but bigger obviously, in the sense that football will likely be followed nationally at the professional level but really only played regionally at a high amateur level.

From a college football standpoint, I think this clearly most affects the Pac 12. HS Football participation in California is declining at a time when overall HS sports participation is increasing. Missing a year for covid may just accelerate this decline. USC is always only a coach away from winning NCs, but beyond that, I'm really not bullish on the Pac 12 top-to-bottom being able to match the SEC or Big10 in terms of quality anytime soon.