If you throw out incremental thought on this and understand that the big money comes from the demise of others, then you can start to see the picture and how there aren't many more teams to be added.
The BIG and SEC are going to add a few more teams and stage their own playoffs. First, is the BIG TV deal. It was reported at a possible $1B/yr before USC/UCLA. Now we hear $80-$100M per team which would be $1.3-$1.6B. The way that really gets bigger is if the other conferences are relegated to second tier status and that happens by making the Power 5 the Power 2.
Those contracts get bigger when they are the only two that matter. And to be the only two that matter, they stage their own playoff estimated $1.9B or another $50M per team. Nobody is going to improve on $130-$150M per team so any additions are about product.
We are at 32 teams and there are really only four more that really matter in settling championship history. Notre Dame, Florida State, Miami, and Clemson and two marginal in Oregon and Washington. You add in those teams and every champion with the exception of Washington in 1991, Colorado and Ga Tech in 1990, BYU in 1984 (does this even count), and Pit in 1976 are accounted for all the way back to 1945 when Army won it all. The only BCS game participants not included were Oregon in 2010 and 2015 and Va Tech in 1999. The only other teams to make the 4 team playoff were Oregon, Washington, and Cincinnati.
If you add in Oregon and Washington, then you are only leaving out a handful of contenders over the last 60 years. That's 38 teams, 19 in each conference with very little compelling reason to add beyond that. Probably pick up a few to get to an even number (Stanford, Oklahoma State), but its difficult to come up with value for more because there isn't a market out there big enough to increase these payouts and few strong traditions or rivals left for the teams that are in.
