My vision of Texas is anchored by several things: First, I've lived in several different parts of Texas several different times. Second, I've traveled extensively in Mexico, by bus, car, and backpack. Third, I'm a student of history.
Putting these pieces together, I come up with this: First, the Anglos and Mexicans in that region have a long history of mutual animosity. Secondly, the Mexicans (as recent polling data clearly shows) believe that the SW is morally part of Mexico. They believe that the land was stolen from Mexico by force of arms, and they still reject the idea that the region isn't theirs by right.
As for history, very seldom, if ever, does a massive demographic shift of this sort take place without political upheaval, usually accompanied by violence. As we speak, Anglos in Tx have probably slipped below 50% of the population. In a short time, Mexicans will move above 50% and become the absolute majority in the state. If history is any predictor, this will result in a drastic change in the very fabric of Texan society.
Each time I've moved to Texas, I've been shocked by the change that has taken place since the previous stint there. Mexico is, without a doubt, a corrupt, filthy, narco-republic. With the possible exception of Taxco (and inside the walls of the resorts), I've never seen anywhere in Mexico that I would consider a nice place (clean, safe, etc).
Traveling through Texas, especially the border region, it is clear that the Mexicans are bringing Mexico northward with them. The idea that Texas will remain as it was when the Anglos were the majority is merely whistling past the graveyard. The colonias in the border zone are pure third world.
There is a possibility that Texas won't suffer an upheaval, but will rather settle into a situation similar to post-colonial africa. The majority of anglos will engage in white flight. But, a small anglo minority will remain in most cities, living a rather nice life in walled neighborhoods while the rest of the region outside drifts to its pre-colonial level.
This situation is currently occuring in San Antonio. For all intents and purposes, SA is a Mexican city. But, there is a region in the NW that is mosly post-colonial Anglo neighborhoods. The seem to be happy with the situation.
I've lived in a few third world countries...among the post-colonial ango ex-pats....its not so bad.