I think south Austin is probably likely or maybe a smaller location near campus. It sounds crazy in this day and age, but when I was at UT there were several arcades near campus that seemed to do well. I think opening up on the drag where LE Fun used to be would do a ton of business. I used to stop in there all the time walking home from class or the library around 1997-2000. It might cannibalize their main location some, but I think limiting the size and games to the mini-Pinballz would still leave plenty of draw for the main location.
After that, who knows between Houston and Dallas. Houston has some competition with joystix, but that's only 2 nights a month. I remember them advertising at the Houston show right before they opened, and I'd love to think they have connections here that would bring one here, but Dallas seems to be just as good an option.
I know some good local commercial real estate guys here if they need some help though! Just sayin'.