They don't necessarily need to "secede". I think the Super 4 would argue that they created a new BCS, funded it themselves through TV contracts, and then set the rules. TV networks co-op the championship but stop short of forming a new "NCAA". Meanwhile the networks are free to sign deals with the Sun Belt's of the world, and the bowls are free to invite any teams w/ however many wins they require. They'd say it's market-driven structurally.