Well, the networks aren't likely to argue for 64, and maybe not even for 48. There is enormous dropoff in average viewership from the top 10 programs to #40, and the networks just care about viewership. Massive numbers of people still watch Michigan, Ohio State, Alabama, Penn State, Notre Dame, Texas, etc. even when they have four losses, and you get mega-rating games more frequently by making the big brands meet up more frequently. When you get to teams like Virginia, Maryland, TCU, Syracuse, Cincinnati... ya the networks won't see those as necessary. Very little bang for your buck.