That's an interesting assertion but I believe there may be something ignored in your analysis. Abortion.
Latinos generally are opposed to it, so given that, their population will grow at a faster pace than whites and blacks, generally speaking. Indeed, I do believe latest projections have Hispanics/Latinos as being the new "majority" in the US by 2020.
So really, taking this into account, whichever party Hispanics enter/take over will be ruled by them, and the blacks and whites are the ones that will take a "secondary role".
Also, several experiments in some really nasty parts of India found out women wre willing to begin counseling their reproductive habits simply by being told 'you don't need to have so many kids'.
Then, there are the marriages across ethnic lines ~ the chiquitas are always going to be more interested in the guys with good jobs than the homeless campesinos still wearing village costumes.
ALWAYS!!!
I don't think those ol'boys have it in them to deliver the goods.