Good point, there are two groups on the have nots.
P5 schools:
Washington State is a case study. If they are left out, what does their fanbase do? They could play in the Mountain west or the could drop to FCS. Their hardcore fans will still follow the team. Their casual fans will either find another college team to follow (unlikely it is a former pac team) or they will drop college football altogether. My guess is the second. I think UW ratings will drop because WSU fans will have no interest in even casually watching their games.
So yes, there will be a reduction in viewership, at least in the near term. Twenty years from now WSU alum may watch UW games, but i doubt it will nearly as many as watch today.
Dropping the Wake level fanbases is barely a blip. WSU/OSU are big schools. It would be far worse in football centered schools like GT/FSU/Clem if they were left out.
Non-P5 schools:
GaSo is and App St are case studies. Why move up from where you are competing for championships to where your chances are infinitesimal? Why take on the extra expense?
From espn’s perspective, did the FBS viewer base increase beyond just the GaSo fans watching their own games?
Will GaSo fans watch games from a league where that aren’t allowed to compete?