It's pretty simple, actually: If LSU wins out, they're in the BCS title game. The Kansas-Missouri winner, should they win the Big 12 title game, are in, too. That's the cleanest version.
If the KU-MU winner loses in the Big 12 title game (or LSU stumbles), the other spot(s) will either go to West Virginia or Ohio State.
Five teams for two spots (with that number dropping to 4 as soon as we have a KU-MU winner next Saturday). That's what we've come down to. All hail the Red Raiders.