So, I did some Google searches..
the Human Rights Campaign - a totally liberal outfit - puts their estimation of transgenders between .25% and 1% of the population.. They also butter their number by claiming many of these people would have reassignment surgery if they weren't too poor, scared, etc etc etc .. So, this is the best case scenario for the transgender alliances.. If most of these [oppsex] trapped in a [sex] body people still look like their original sex, then the ID card wont be a problem.
However:
Other figures put the number much, much, MUCH smaller at 1 in 30 thousand males and 1 in 100 thousand females who will proceed with sex reassignment surgery. When one considers the 1 in 30K number, and considers a population estimate of 25 million people in Texas, there are about 834 'disenfranchised' people to consider. I suspect out of that 834, most will get new ID cards, drivers licenses, etc. as having a photo ID that doesn't match may get the person into more trouble than being outed at the polling place, such as a bar, liquor store, or police pull-over.