I'm not assuming that the champion of one of those teams automatically gets in because there are obviously 5 conferences, but I do think it is unlikely that a 1 loss non-champion gets in over a 1 loss champion from those conferences unless it is clear the champion played a terrible schedule or the 1 loss non-champion played a murderer's row. That said, I don't think the 1 loss can be in the conference title game either, so if Alabama and Auburn are unbeaten (except for the one that lost to the other), I think that is where you might see a 1 loss team having a shot at the 4th spot especially if that team is Auburn (they are at Kansas State and have South Carolina and Georgia from the East). So if they are both unbeaten for their game on November 29th, I think there is a good chance they both make it in (assuming the winner actually wins the SEC).
So the way I see it this year
1. Florida State
2. SEC champion
3. Big Ten champion
4. SEC #2 or Oklahoma
I think the Pac 12 is very deep with no real great teams, so I don't think a team comes out of it with less than 2 losses (which likely isn't getting in the playoffs). Outside of FSU, the ACC has no shot, and because of that I think FSU goes unbeaten rather easily. I think Michigan State or Ohio State have the schedule and enough skill to finish unbeaten (or with one loss), so I slot them in at 3 (this is especially true if MSU goes to Oregon and wins on Sept 6). The 4th spot will come down to whether or not Oklahoma does what it should and wins out (or loses just 1 early to a good team) if they do they are in, if they don't then it will go to a 1 loss SEC team (if such team exists and if the Pac 12 champ).