Right now the immediate danger is John Sharp winning the KBH Senate seat in a special election early in 2010 and the Democrat takeover of the State House of Representatives in Nvember 2010. The GOP lead there is now 76-74. If TX does turn Democrat, GWB will have played a major role. By being so noncommital, he helped the Democrats. Dorothy Ann Willis Richards must be laughing in her grave.
If you define "danger" as about a 1 in 10 probability, then yes, there is a danger.
Look at the CNN exit polls from Texas in 2004 and 2008. The demographic shift you are talking about is not playing out in practice. The numer of conservatives and hispanics voting was the same each year. The only difference in 2008 is that less self-identified conservatives voted Republican.
Also, with regards to your other posts on religion, a majority of Catholics in the northern states vote Republican, despite heavy Democrat majorities in the Protestant communities. So I think the relevant identifying characteristic that determines Hispanic voting behavior in the southern states is more racial and economic than religious.