As Hispanics integrate, they will be lumped more into the existing racial categories. I'm Cuban, but look indistinguishable from an Italian or Greek person. Plus, like immigration from Ireland, Italy, Germany, etc, immigration from Latin America will eventually slow, and may be doing so already.
I think this is a good point and may be one of the reasons that Hispanic/Latino is not actually considered a race but an ethnicity. I think that Hispanic Americans are likely to begin assimilating into the culture in the same way earlier waves of European immigrants were able to. Many people who identify as being Hispanic have virtually no outward physical characteristics to distinguish them as being such.
