If Oregon and USC/UCLA win out, those schools would meet in Las Vegas for the PAC championship. If this is the case, the winner of that game would probably get the #4 spot.
USC: Colorado, @UCLA, ND
UCLA: Arizona, USC, @Cal
Oregon: Washington, Utah, @OrSU
UCLA has the easiest schedule there, by far.
Oregon has the toughest maybe. That Civil War game.. you just never know.