My timeline is in 10 years.
I see Texas St. making it in the same way that Texas Tech did. I don't rmemeber Tech ever being a force in football until they joined the Big 12 and hired Leach. Before that, I remember Tech being about the same level as New Mexico St. They were really never a force and Usually lost everytime they played against a Big 8 team.
Texas St. is different than TCU and SMU because they are a much larger school, and are a public university. I know they are leaps and bounds away from their beauty school beginnings as Southwest Texas University. From where I am standing, I see them making a lot of necessary moves to make it at the next level. They are even become more of an option for kids that would otherwise choose TCU, SMU, Baylor, and Houston.
My big question is will they be able to raise their academic standards enough to be included into the Big 12. I think they will have to build themselves in a mid major conference for about a decade taking kids that may not qualify for Texas and aTm until they can actually compete at the BCS level.
Again, I don't understand why Texas State is supposed to be able to accomplish what teams like Houston and North Texas haven't been able to do. You're description of Texas State is accurate, but it also applies to 10 schools around the state, what makes them different? Look at the list below of the top 10 colleges in Texas by size. Three are in the Big 12, Texas State is one, so there's 6 other schools, if those teams can't build a powerful football program with a 100 year head start, why is Texas State gonna be able to? There's simply no evidence to suggest they're going to be able to grow into a competitive program in a conference like the Big 12. I removed the names of the teams on the list below to at least try to take away the bias, it shows that Texas State isn't the only school with a large student body and alumni base.
Top 10 as of Fall 2008[1]
1 50,006
2 48,126
3 36,104
4 34,795
5 29,125
6 28,585
7 28,422
8 25,070
9 20,458
10 17,577
You're severely over estimating New Mexico State, they're one of the all time losingest programs in college football history. They're Kansas State pre-Bill Snyder, only without ever getting a coach like Bill Snyder. Texas Tech isn't an elite program, never won a championship, but we do have a winning record all time. Putting those two teams in the same category is just a poor, poor comparison.