I don't know. Obviously some amount fans, like yourself, would watch less. But is it a big enough % that the TV execs would care? Do they think they could make up that difference, and then some, over time by appealing to new fans?
The NFL only has 32 teams. Their fandom and ratings in the U.S. is not based on just fans in those 32 cities. They draw fans from all over the country that 'adopt' teams to root for that are not based on the city they live in.
College football has way less fans than the NFL. However, a TV exec could look at that as a growth opportunity: There are millions of NFL football fans that aren't college football fans - let's get even a fraction of them to watch college football. And they don't need 70 brands to do that. As noted, the NFL only has 32 brands. Get the Top 48 brands into two 24-team leagues (SEC and Big Ten) and then market the heck out of it. There is probably room to market better if focused on just these two leagues than marketing a bunch of leagues consisting of 128 FBS teams. The current product is diluted.
The only hope for schools like Pitt is that the Big Ten and SEC need broken up or reconfigured to shed some dead weight. Schools like Vandy, Indiana, Rutgers, etc. could eventually be dumped like Wash St and Oregon St just were. However, if you replace Vandy, Indiana, Rutgers with FSU/Clemson/Notre Dame...there still isn't room for Pitt. They would first have to cut deeper like Miss St, Minnesota, maybe Northwestern or Purdue, then we'd still have to beat out UNC, UVA, Miami, VA Tech, Louisville, and several Big 12 teams.
So even at 48 teams, Pitt isn't getting in. 70 teams definitely should be what Pitt fans root for, but I don't think the TV execs need 70 to make big money. The hope for 70-80 teams is that the TV execs value having more inventory. While Pitt-Syracuse is not going to make the Top 50 watched games list, it can still draw more eyeballs than reruns of Designing Women on Lifetime. Look at how even the crappiest of Bowl games do great ratings compared to what else is on at the same time (vs comparing the ratings to other football games). Football games get ratings.