Asians and hispanics are intermarrying with whites too quickly for there to be solidly white/minority blocs by mid-century.
I live in Southern California and I can state that this is unequivocally true. I'm surprised that it took a Canadian in this thread to correctly point this out.
Hell even half Mexican half white kids look pretty White (same is true for half Asian half whites). People seem to forget that his country started off as a WASP society and that the Irish, Catholics, southern and Eastern Europeans were originally deemed as others. Over time they were absorbed into the White majority. The children of Whites and Hispanics/Asians will likely follow suit.