Teams change conferences. It's a fact of college football life. The more football-obsessed members of the Southern Conference left to form the Southeastern Conference in the 1930s. Conference USA has had almost as many different members at one point or another (24) as years of existence (25). Forty-two schools have called themselves members of the WAC at some point, with a 43rd (Southern Utah) on the way.
Never in the history of college football conference realignment, however, has there been a potential earthquake the magnitude of Oklahoma and Texas possibly leaving the Big 12 in favor of joining the SEC.