I've not seen the Texas legislature challenging it. They PASSED it, by a pretty solid majority, Perry signed it. This wasn't some executive order. This was in 2001, so that was when it appeared people supported it.
They haven't passed a bill recinding it. The people haven't voted them out of office.
But recent polling indicates the people of texas, when asked, are opposed to the in-state tuition for illegals, by a wide margin. So it seems clear the people are no longer supportive of what was passed in 2001. Makes you wonder why the legislature hasn't tried to repeal it, maybe they will next session.