Wow. Fascinating stuff. I had heard bits and pieces of this sort of prediction in various places, but never as coherently as this. This must be disturbing and even frightening for some Americans. No wonder the Religious Right is so strident: if these figures are true, they may be headed for utter marginalization. Which, in my books, would be just fine.
Or, are they...?
One thing I didn't see discussed (but which is discussed in the very similar Canadian work The Big Shift), is the theory that many new immigrants hold strong religious beliefs and are socially quite conservative. Hispanics and Asians, the two groups headlined in the Pew study, are anecdotally social and religious conservatives. In Canada we see a similar theory around South Asian immigrants. The theory holds that, for example, issues of women's rights, gay rights, a secular society, etc don't necessarily resonate the same with these folks as they do in middle class, liberal European-background society.
The interesting thing on the religious front is that the vanguard of religious and social conservatism might pass from white, old stock middle class and largely rural Protestants to middle and lower middle class immigrants in large urban centres.
Could the Republican Party (or its successor) become a party of younger non-white immigrants, while the Democrats become a shrinking faction of aging white, liberal, middle and upper class folks?