This may be for the future, but it sure won't be the case in the 2016 election.
Not even the most optimistic Democrat strategists think HRC can win Texas.
However, it does show how the Democrat's "open borders" strategy is working.
You need to ask yourself, Why do immigrants in Texas vote Democrat?
Because they are philosophically liberal?
Because as immigrants they are most likely to benefit from generous social programs?
Because as Mexican immigrants they are more inclined towards policies that treat illegal alien relatives rather softly?
In the short term (and this is a relative term) Mexican immigrants in Texas are likely to vote for Democrats (People almost always vote for their self-interest which is a good thing), but contrary to what many bigots might think, Mexicans are a hardworking people who value family, religion and the rule of law (unless it has to do with immigration). In time, as they prosper, their interests will be more aligned with the conservative policies that were a part of their ideology when they came here.
So in the (long) short term, Mexican immigrants may indeed change Texas to purple or blue, but eventually they will revert back to red.
The blue supremacy is highly dependent upon a permanent underclass looking for the State to provide them with an easy if not prosperous life. For all sorts of reasons, (not all or even most that they are responsible for) the African-American community has had a terrible problem with breaking free from this dependency status. Asian-Americans haven't and I don't think Mexican-Americans will either.