I agree with the gist of what you said, but do you not think upward socioeconomic and educational mobility among multi-generational Tejanos (or older immigrant waves) would result in college-educated suburbs also becoming progressively more Latino over time? I don't have a solid grasp of demographic shifts in Texas Triangle suburbs, but I would expect some of the long-term D shift there to be due to urban flight and racial diversification (from Latinos) alone.
To some level, yes. But I think it would also be a mistake to conflate upward socioeconomic mobility with upward educational mobility. As the value of a college education drops and manufacturing jobs are reshored, there really is no economic incentive to attain a higher level of education (at least in the sense that we think of education today), and that incentive will only get stronger as wage growth in blue collar professions outpaces white collar professions during what is likely to be a prolonged period of high inflation. Given time, these changes will again change the character and the values of the suburbs.