By definition, the top revenue-generator in each conference. For the Big Ten, I assume that's either OSU or Michigan. USC in the PAC. LSU or Florida in the SEC? Conferences have some benefit, even for football--scheduling, maintaining rivalries, BCS berths--so if a school's only two goals are optimizing revenue and being in a conference, it would make sense for the top programs in each conference to withdraw and form a conference together. There'd be more money to split in a coast-to-coast conference containing OSU, Michigan, USC, LSU, Florida, Texas, Oklahoma, and Alabama than anyone would know what to do with.
If that happened, I'd expect the "new" top schools in the old conferences to start doing the same. The "second-best" conference could consist of Penn State, Georgia, Nebraska, Tennessee, Virginia Tech, Oregon, Wisconsin, and Florida State, for example. And on down the line you'd go until you get to a "bottom of the barrel" conference of Vanderbilt, Washington State, Northwestern, Mississippi State, Indiana, Rutgers, Wake Forest, and let's just say Iowa State for posterity's sake.
That's my nightmare scenario. I would be surprised if the political powers-that-be would ever, ever allow it to happen, but I wouldn't be surprised to see some elements of it occurring (more ESPN-influenced "marquee" television games, separate conferences for football and non-football sports, conferences with less and less geographic cohesion [which we're already seeing], etc.).