At least the whole world is gradually becoming democratic and capitalistic. That's one form of homogeneity, at least in expectations if not ethnicity.
Capitalism runs off of inequality of all sorts. Capitalism's entire history is filled with instances of the ruling class systematically serving up xenophobic and racially divisive propaganda (in order to justify expanding imperially, in order to justify inexpensive labor, etc.), with no sign of slowing down. As such, I can find no evidence that cultural tranquility is possible under the global capitalism. The inequality that capitalism continues to deliver breeds dangerous ideological heterogeneity between the people of the working class.
Someone hard-working with a 130 IQ versus someone depressed or maladjusted with a 90 IQ are, in fact, in entirely different classes. It isn't "dangerous" to admit that, it's simply reality. Capitalism does a decent job handling those extremes.
> Someone hard-working with a 130 IQ versus someone depressed or maladjusted with a 90 IQ
Capitalism doesn't do a "decent job handling those extremes," it does a fantastic job creating those extremes. The latter person you mentioned is either highly exploited and/or rejected from society and given a tragic, humiliating life. Our capitalism is divisive, unjust, and destructive.
Capitalism just deals with the results, in this case human capital.