It never really was that. When the Spanish named it Tejas, it was incredibly sparsely populated compared to everywhere else they were colonizing. There were the some Caddo confederations, the Apache, Comanche, and Karankawa but those groups moved around and saw themselves united largely by language rather than region. Much of eastern Texas was considered uninhabitable by the natives mainly due to it being unlivable swampland with frequent malaria outbreaks and poor areas to hunt/gather. And that eastern region is what became the land of horrors we know today. (Houston, Dallas, Beaumont, Galveston, etc)

When Mexico secured independence, the region Spain designated as Tejas was combined with another region to form the federal state of Coahuila y Tejas. And even then, it was still sparsely populated and had a lack of any proper identity. Mexico wanted the land used though, so they paid a bunch of American slave owning dipshits to come settle the land, included among them Sam Houston and Steven F. Austin. Those settlers were the first to actually grant Texas/Tejas a kind of regional identity. And it’s one of the great tragedies of history that Mexico lost that war and the subsequent war with the US.

So the creation of a modern Tejas would be a new project inherently built off stripping it from its white colonizer history, its Spanish colonizer history, and building something kind of new out of its modern, majority Latino population. So in a sense you might say hopefully Texas will become Tejas for the first time in the near future. We can hope something can be made of this utter mess of a place we have.