It’s a good question that does not have an answer.
But if you had to guess which direction interest would go, it would likely be down.
Realignment and the consolidation of power, influence and money into two conferences will be a headwind for every other program. Fan interest follows success; the current set up makes success unlikely outside of the B10 and SEC. (Even inside of those conferences, you are talking about a handful of teams capable of winning consistently.) The number of schools that will realistically have a shot at winning a championship will keep getting smaller, even as the playoffs get larger.
Contrast that with the NFL where the only impediment to winning is your front office. Every fan of every team, other than Viking fans, believes that their team can win a Super Bowl at some point. There’s nothing structural preventing them from doing so.
If you wanted to devise a system where college sports bleeds fans and attention, this is exactly how you would start.