Couple of things with Saban.
One, there is always the possibility of shady sh*t going on at Bama that can get them nailed. Texas is much better and "cleaner" in how they do things than Bama. Bama is ALWAYS involved in some shady sh*t, and despite the NCAA turning a blind eye to most of it, every few years like clockwork something happens that they can no longer ignore and have to come down on them. So the idea that there could be trouble brewing is not outlandish.
Two, Texas can afford to probably pay him more. Yes initially it would be a ploy to get more money, but you never know, Texas can go HAM and offer him something totally unheard of in college sports. Its not out of the question.
Three, he has a much easier schedule at Texas, less stress, and easier recruiting environment, and can probably cruise at Texas a lot longer and will less pressure than at Bama. Despite all he's done, if he has 3 mediocre seasons at Bama, those idiots will be throwing a sh*t fit saying he's "lost it". After what Brown has done at Texas, Saban could milk that gig for a decade or more with his eyes closed.
Four, he's not going to have AJ McCarron anymore. Same as with *** losing Tebow. Saban may figure once he loses his smart "offensive general", he's going to have some rebuilding to do. Why not leave Bama on top, vs have to hope he can replace McCarron with another great QB, which is never easy, and maybe have a few years of struggling. He may feel he's done all he can at Bama and can go out like a boss.
Personally I think he stays at Bama, but I can see some scenarios where the Texas gig might look appealing to him. I would not TOTALLY rule out the possibility.