Considering the difference between societies, in fifty to a hundred years their could be a larger gap between Jews & Asians, and Europeans, as Japanese, Koreans, and Chinese, and, tmk, Jews, continue eugenic cultural practices, while Americans and Europeans extend upper-class abortions which can lower our future group-IQ.
I think the number one factor that is contributing the most to "selective areas" of homogeneous behavioral practices-is language. The last I read, the Philippines has 250,000 American expats living there-that is just Americans alone. Filipino's are very affluent in the English language and familiar with Western culture. Years of Chinese trade, five hundred years of Spanish rule and then American occupation; it is very rare to see a truly native Filipino now. I think we are going to see "pockets" of homogeneous communities mixed between certain subsets only. The reason I say subsets (I hope I don't break some rule here), is because from observation, I have noticed that most Filipinos prefer interacting with Caucasians or other Asians exclusive. Even reflective in their buying habits which include skin whitening creams, soaps and lotions of every description. The Filipinos are a very adaptive and mobile people as well, with eleven million of their people working as OFW's (Overseas Foreign Workers) around the world. This does happen among other racial groups as well, but not to my knowledge on the same or an equal scale as Filipinos.
I think the number two factor would be access. There is great difficulty in wading through the required documentation and requirements just to live in a country other than that of your birth. Even though we can physically get to those destinations quickly, the laws of that land apply, which as a general rule for some, does not promote homogeneous acceptance. It is not until we become a truly border-less society as a whole, before large amounts of homogeneous behavior will then be realized. Of course we still have to deal with racial prejudice and religious indifference as well.
In wake of no catastrophic human event, homogeneous world society is a very long way off, in my opinion.