Anecdotally my ward west of Ft. worth is taking 30 plus people to the game, I can't imagine the LDS enclaves of Southlake, Colleyville, Frisco, McKinney and Plano not taking many more. Then, add Austin San Antonio and Houston being at most 3 hours away and I would guess 10-15k might be more appropriate
I think the the Big 12 schools will be thrilled at how BYU fans travel to in conference games