If Iowa and/or Oklahoma St. win out, they will be in. Plain and simple, the committee will not ignore an undefeated power-5 champion.
Realistically the only open slot then would be the one Alabama is in, which if Clempson, OkState, and OhioSt/Iowa is left undefeated would go to either the Tide or Notre Dame.
Right now, it seems to be Alabama, but with Ole Miss and LSU continuing to lose, Alabama won't have any victories against ranked teams (the committee looks at where they're ranked at the times of the rankings, not when they played, they said as much last year), and their loss would be to an unranked team, as opposed to Notre Dame's single loss to #1 Clempson.
So Alabama needs Notre Dame to lose, or Florida to beat FSU to make the conference championship game look good. Course if Oklahoma St or the Big Ten champ trip up, then both the Tide and Irish are in, assuming they each beat Florida and Stanford, neither of which is a given.
Who know, South Carolina might even beat Clempson, though it would be more likely that North Carolina would in the ACC game, if the Tigers are too lose.
Don't you just love end of the season guessing?