I agree with GD that the Federal government would likely let a state go rather than go to war at this stage. We live in a very different time, we also won't see a draft anytime in the future, or a World War, so those are all positives.
But realistically, I doubt you are ever going to get enough Texans to go along with a plan to secede. I tried to see what data I could find on it, and this is what I found:
http://dallasmorningviewsblog.dallasnews.com/2014/09/a-third-of-texans-support-seceding-from-the-union.html/
So I mean a third is a pretty good number, but that's just a poll, and it is much easier to say you want to secede than it is to follow through. Would there really be enough pros to outweigh the cons? Would it really even make much of a difference?