Trust me, this is one battle that Texans would be better off losing...there is NO MARKET for the train, unless you consider someone that lives in downtown Houston needing to go to downtown Dallas.
Otherwise, simply fly - two airports with full-up supporting infrastructure (i.e., rental cars, easy freeway access to get anywhere in either city, etc.). Or, for people that want to spend less, spend a billion or so (at the very most) to widen I-45 and give Megabus some help in locating their stations.
I would think one of the things that would put high speed trains ahead is if they would allow CCW on their trains.
I know if there was a comparably priced, straight through train to Florida that would allow me to carry I would take it.
I will not fly unless going over seas. And that is one heck of a drive.