I think Oregon has the best chance out of the three of losing. Based on one more game remaining then the others, and their rivalry game this year will be especially tough in Oregon St.
The road for Notre Dame goes through USC, at USC, so that won't be easy either.
If Notre Dame and Oregon win out, they will have two common opponents.
K State, at least on paper, appears to have the best shot.
If only one out of three loses, no way the SEC gets in. Two out of three, and there will be some controversy, but the SEC will sneak in.