For the last few years, it's obvious that Alabama and Clemson are way above the rest of the college football world. It won't always be like that since the main reason that's the case are head coaches Nick Saban and Dabo Swinney. Before Saban, Mike Shula was 29-21 at Alabama, while at Clemson Tommy Bowden was 43-32 before Swinney.
When Saban and Swinney moves on to someplace else, and Alabama and Clemson come back to earth a little, there should be more parity. There's always the chance that another coach or two will dominate for awhile, but more likely the playoff race will be wide open.