The very same census report projects that as far out as 2060, 68.5 percent of the population will be white. It’s just that a reasonably large share of the white population will be partially descended from Latin American immigrants. A further 6.2 percent of the population will belong to “two or more races,” with a large share of those likely identifying at least in part as white. The difference here is between an exclusive and inclusive definition of whiteness.
There was a time when those who were Irish, Italian and Slavic were not considered white. This is in keeping with American traditions in letting people be white over time.