I think Trump will do very well in Texas, though Cruz will win handily. Lots of Reagan Democrats that will vote Trump instead of Hillary/Sanders in the primary.
Trump's basically flipping the largest finger at DC, something the average Texan appreciates.
Having said that, Cruz has had a ground game established in Texas for years. Trump won't be able to overcome that.
Cruz will get fewer GOP primary votes in Texas than Romney did in 2012.