whoever said "south africa" was spot on
the sort of radical population change that the op is referring to is already occurring in the american southwest, where you have traditional white upper and middle class populations, in either static or negiatve growth, being quickly (in historical sense) being surpassed by a burgeoning hispanic population. the numbers, if you look at them, are sort of staggering. phoenix, AZ has gone from 8% to 35% hispanic in under 20 years. 2 years ago, over 50% of the babies born in california were hispanic. these numbers are only increasing, and at a fairly amazing rate. this is what happens when you "pit" a static population against one that is increasing virtually exponentially.
for whatever reason (religious, cultural, etc.), outside of the traditional bargain-basement working class type mold, hispanics haven't adapted well to the american system (when compared to Asians and Indians [esp. in teh state of California, where the UC is in a state of meltdown because hispanics just aren't getting teh scores to get into the system], teh differences between minority immigrant populations immediately becomes stark). the reality remains that 3rd and 4th generation hispanc-americans gennerally occupy the lower rungs of society. in arizona, tremendous $ is being spent attempting to get predominately hispanic high schools "up to speed," yet the % that don't graduate from high shcool only increases with each year. the emphasis just isn't being put in education in hispanic households, and as a result, the placement of hispancis amongst the lower rungs of american society remains relatively constant.
sooooooooo you have a rapidly-breeding, under-achieving immigrant population that is quickly swelling the ranks of the american southwest. everyone knows what is going to happen next. by the time we're old and gray teh southwest with be full of "brown cities" with enclaves of white communities hidden away behind tall gates; teh whites that stay will, of course, be generally afraid (like SA), and will hold on to whatever power may still have (a human condiiton, as opposed to a racial one). there will be acrimony, fear, violence, white-flight, etc. or maybe it'll be a washington, DC type situation, where the various racial "factions" coexist, but only in very separate and distinct quadrants. any out-of-bounds after-dark wandering will result, inevitably, in some sort of violent episode.
seems like a positive outlook doesn't it?