Major college football will most likely be a closed shop of 30ish schools playing only against one another with an NFL-type schedule and playoff, heavily concentrated in the South. All the games will be on a paid subscription service a la NFL Sunday Ticket or the Premier League in the UK. Attendance will be okay at the surviving schools, softer than now, but not so bad it's jarring. There will be formal parity enforcement mechanisms by then too, a recruit draft wouldn't shock me. The current power 5 schools that don't make it will probably drop football entirely rather than bother with sub-major status, especially the ones whose stadiums sit on valuable real estate. I could see Illinois in any of the three camps to be honest.
It will be a passionate niche, but a niche, and ever more obviously so. Football participation in general will continue to decline and more of the players will be foreign. NFL attendance and ratings will also be softening. We'll look at the sport of football then a lot like we look at the sport of baseball now.
Non-revenue sports will be cut back significantly as donor money flows to NIL consortia (the NCAA will outlaw those in the next year or so, and the consortia will sue and win). Basketball will probably be more or less fine. The whole spectator sports industry will go into recession as soon as the broader market does, but college basketball is on pretty firm footing.
It's not the apocalypse (except for the programs that fold I guess), but it's a smaller, weaker landscape. Some of it was unavoidable due to economic and football-specific factors. But in, say, 2008 the Big Ten was well positioned to be as robust against these challenges as any entity in the whole sports industry, in a position to gain where other major leagues lost. It chose a different path and will be an empty husk of a legacy brand name at best soon enough.
