Seriously, what’s to keep these 16 teams from leaving their current conferences and forming a brand new league?
I'll bite: these are college football's power teams in no small part because they're almost always powerful (in terms of wins and losses). You put all of them in one mega-conference and don't let them play anyone else, someone is going to finish with only two or three wins - or fewer. And there's not going to be a player draft designed to help losing teams catch up. If, say, Florida State winds up becoming the Super League's football equivalent of what Vanderbilt is to the SEC, what happens to its brand? Heck, would its place in the Super League be secure? Would recruits really want to go play there instead of a winning non-Super League school? So, to answer your question, risk aversion will keep some of these schools from taking this sort of plunge.
I do think there's a democratic element of college sports that would also be left out under this sort of structure. I often like to think about college football and basketball in America the way that I think about soccer in a country like England: in the latter, you have your big clubs (Man United, Man City, Liverpool, Chelsea, etc.), but you're also bound to have a pretty decent club in a lower league relatively close to you that you can support on a local level. And with the right management and a few breaks here and there, your club could get to the big time, and - cf. Leicester City - maybe even win the proverbial national championship. College football is still like this, sort of...and college basketball is definitely like this, in ways that the big city franchises of professional sport basically aren't. This Super League concept would basically make college football the NFL, except with most of its franchises located in (relatively) rural areas. Would that affect college football's popularity? In the short term, probably not, but in the long term? I don't know, but it's something to think about. (And I haven't even touched upon the fact that the pursuit of undefeated seasons and big upsets - not just your App State over Michigan, but also your slightly more run-of-the-mill Indiana or Purdue over Ohio State - are part of what makes college football so riotous to watch week to week. If CFB becomes the Rural NFL, the character of the product on the field becomes very, very different.)