They'd have to have a name change for it to work in San Antonio. (I didn't read the article, so not sure what all was discussed in it.) The majority of Texas would stay Cowboys fans, but if you rebranded the team as the San Antonio Coyotes or something, I think you could definitely convert some of those southern Texas fans a lot easier than it was for the Houston Texans to win people over that were either still rooting for the Oilers as the Titans or were always Cowboys fans.
Even if they were still Cowboys fans, it's not like it would be hard to sell out the stadium to a football game in Texas. Living in Austin, I'd rather drive down to San Antonio than over to Houston or up to Dallas. I don't see them letting the Raiders change their name, though...and the San Antonio Raiders just sounds stupid and really doesn't fit in with the culture or community there.