Looks increasingly unlikely that the Big 12 or PAC 12 will have a representative.
I think the Big 12 will, simply because they will be perceived depth in the conference. If TCU run the table from here, they'll be in. They are a well balanced team, and they'll take the Big 12 title by beating Kansas State (who will be ranked, as could the Mountaineers when they play) with their one defeat being a bizarre late collapse (to another very good side). They'd be taken over a second one-loss SEC team I reckon.
The whole Big 12 situation is amusing. When you think of the mayhem in the conference a few years ago, when it looked like the whole thing might collapse, and now look at a schedule that includes Kentucky State, Oklahoma, Baylor, the Pokes, and TCU. Even funnier when you consider Texas's complicity in the confusion, and they money they climbed over corpses to get, and for now they're a nothing player in the conference.
Sparty are creeping back in, and assuming they beat Ohio State they'll get either Minnesota or Nebraska in the conference title game. They've already beaten Nebraska, so I'm not sure what value lies in either game other than the conference title, but that defeat to Oregon could cost them. Especially if Oregon win the PAC12 with just one defeat. Playing the Big Ten schedule just doesn't offer many chances for highlight wins these days.
I think, in terms of the college scene being wide open, this is probably the worst season to start a four team playoff as the decision will be impossible. I mean, if FSU go unbeaten and win the ACC, how do you leave them out, especially as they are defending champs? And yet, the only good win on their entire schedule is a stumbled home fixture against Notre Dame. That Clemson win, even with the QB situation, isn't going to mean much. They'll be the most overranked unbeaten team ever. I'm willing on a debacle in Kentucky next Thursday, but the open week will mitigate the risk.
You could fill the playoffs with SEC teams, but nobody's going to do that. And first season into the new system, I doubt they'll double dip in a conference, even one as strong as the SEC (especially if the other conference champs are one-loss teams). They'll want four conference champions. FSU and SEC champs are more or less a lock, so then it becomes a choice of two from the other three.
The committee releases their first rankings a week tomorrow. I wonder whether they'll consider the big picture, i.e. if they name a stack of SEC teams right at the top, how will they justify jumping over them later if they don't want to double dip. And if they're substantially different to the AP Poll, that'll be an issue in and of itself.
Whole thing's going to be carnage. Which is great. They're probably already wishing they went for eight teams.