"...that Catholics will become a minority...."

US Catholics have never been a majority in the US. They have always been a minority (except in Louisiana Territory, Central Continental US, pre-1803, when it was part of the French Empire). So I'm not sure what you are getting at. And there is no guarantee that all Hispanics will remain Catholic in the future. According to Pew Researchers, in 2050, only 40% of Hispanics will be Catholic; nearly 25% will be non affiliated; 24% will be Protestant of all traditions; and the rest, "other." So down the road, there will be no great "majority" gain.