Exactly - think of it as an emulsion. The various substances will clump together by their own properties - but they will still be swimming against each other, being all suspended in the same solution.

What would contradict my point is if the people moving were all moving to isolated, self-sustaining communes or becoming hermits. But no, they generally move around more explicitly for work or retirement, both of which require significant interaction with multiple demographics. Now retirement (note not simply assisted care, just retirement, typically into municipalities with majority-elderly populations) is a more interesting case for us because it often results in "aged communities" of (for now mostly white) senior citizens congregating to live out their retirements. Perhaps there are social differences between communities developing around retirement and more mixed residential areas centered around commute to employment or otherwise entertainments and leisure activities.

Excerpts from the concluding chapter of Senior Power or Senior Peril: Aged Communities and American Society in the Twenty-First Century:

Spoiler Alert, click show to read: 
The aged context actually fosters a number of
unique political attitudes and behaviors, ensuring a distinct political
culture in locales with concentrations of older adults. This political
culture includes higher levels of political knowledge, less political efficacy,
more support for safety-net policies, and not exceptional levels
of turnout for elections among older-adult residents.
In this book, I have spent much time and effort on answering the
question of whether there are differences in political attitudes and
behaviors in aged communities that cannot be attributed simply to
the age or some other individual characteristic of residents but result
from the overwhelming presence of older-adult residents in the local
population. The answers to this question are quite consequential for
local and national politics as the Baby Boomers move into retirement
age, providing a picture of either pockets of senior activism and power
or retreatism and powerlessness all over the United States.
First, aged locales are probably places with increased opportunities
for political discussion. Measures were not ideal for measuring discussion
levels. However, we know that the increased opportunities are
present, given the testimony of the residents of The Villages and the
numbers of meeting places for seniors per capita that are available in
aged communities. We can also be quite confident that aged communities
are places with a high density of political resources and information,
owing to the higher rate of senior centers in such places. This
finding may indicate that further concentration of resources likely contribute
to the accessibility of aged cognitive content for residents of all
ages. Although the measures of engagement were not ideal for the
analysis, there is also evidence that political engagement is higher
among older adults in the aged locales.
older adults living among their peers have greater
levels of political knowledge than do seniors living elsewhere. The
association is particularly strong for knowledge related to senior issues
such as Social Security and prescription coverage. However, this relationship
is not apparent for the residents of very advanced age.
Chapter 5 provides evidence for a senior citizenry with cohesive
and supportive preferences for safety-net policies when they reside in
the aged communities. They are more supportive of policies that push
for a wider safety net than are their peers living in other places without
an aged context. These findings make sense, given their greater knowledge
of senior-related issues. In addition, the aged context appears to
have an impact on the attitudes toward safety-net policies of the
youngest residents in aged communities. They are also more supportive
of these policies than are their peers living elsewhere.
Although knowledgeable and unified on aged-relevant issues,
senior citizens living among their peers may not actually be very efficacious
or especially active. These relationships are explored in Chapters
6 and 7. The emergent older adults in the aged communities may be
less politically efficacious than seniors living elsewhere. The efficacy
attitudes of young adult residents are also related to the aged context,
as is the case with their attitudes toward safety-net policies. However,
the consequences may be quite negative, given the lower levels of political
efficacy for young people no matter where they live.
Living in an aged community also has some impact on the political
participation of its older residents, although there is a mixed bag of
evidence. Results for 2000 were consistent with the lower participation
expectations for aged community residents, but results for 2008 were
quite the opposite. Older adults may have the potential for exerting
exceptional participation and force but only in certain circumstances.
However, most of the time, aged places are not necessarily critical centers
of participation, as many people have supposed.
Chapter 2 discusses the two main types of
aged communities (active retired and small town) and the different
factors leading to their skewed population distributions. By accounting
for the size of the population, the median household income of each
community, and whether the local population is increasing or decreasing,
we gain confidence that results from the analyses are due to social
effects related to the aged population of the community rather than
differences in the populations that make up these two types of aged
locales. Past work on the aged context has paid little attention to the
differences between aging communities and aging individuals. The
scholarship of the politics of aging and especially journalism on
the subject too often assume that older adults belong to one massive
indistinct group.
different effects depending on whether an older adult is an
emergent older adult or an adult of very advanced age.
I also examine the youngest voters in society in a few chapters of
the book because this group is often still politically unsettled and only
beginning to establish political predispositions. Past contextual research
led to the hypothesis that the politics of minorities within the population
may be influenced by the politics of those with the greatest numbers.
For the current work, the overwhelming presence of older adults
in aged communities has made an impact on the younger generation
of residents living among them by influencing their attitudes toward
safety-net policies and their political efficacy attitudes—political characteristics
that may be influenced without much direct contact but by
simply living in a place with a certain aged cognitive content.
Many scholars have made
the logical leap, supposing that concentrations of socially interactive
older adults who are generally politically knowledgeable, efficacious,
tuned-in, and able should result in a politically exceptional and powerful
geriatric populace.
This work supports and adds to the less sensational but incredibly
important work that tells a different story. In the aged communities, we
find a distinctive mix of high political knowledge and low efficacy with
unimpressive turnout levels. It is possible that older adults have the
ability to remain engaged and current with political information but
lack the level of physical capability that might encourage increased
political activity in aged communities.
Physical challenges faced by older adults may very well contribute
to this disenchantment with politics, but it is also likely that aged communities
encourage a retreatist and politically pessimistic outlook
among many residents. In many of the communities, there are plenty
of leisure activities to take up energy that do not directly involve politics
So older residents of the aged communities are usually not forming
politically cohesive and powerful blocs of voters.
The results in this book present a case for the capability of older
adults and their potential to become a powerful force in local and
national politics when they are motivated by a threat to their livelihood.
Other work has shown this to be reality in many communities in
the right mix of circumstances. We see this happening frequently in a
pluralistic society in which many groups exhibit high levels of political
skills and resources.



So far the case makes it sound as though elderly communities become both insular (with respect to the mobility of elders themselves) and assimilating in key respects. These respects are not found to be based on individual or demographic differences, nor on the geographic context of the communities, but rather on the "aged context" (being around a bunch of retirees all the time) itself. It also appears that these places are not entirely self-selecting for culture (re: newcomers), but do indeed have assimilating effects on elderly/aged newcomers themselves, which may partly be a function of insularity. Also as quoted above, all these things stand in contrast to characteristics of the elderly distributed more evenly among the people.
However, it's also important to keep in mind that for now most such concentrations in America are overwhelmingly white, which must definitely affect our judgments on cultural assimilation.

In terms of our discussion, the relevance has to be somewhere in the principles. What I see is that homogeneity and insularity would not be enough to reduce multiculturalism, absent some convergent cultural impulse affecting all members/residents simultaneously. In other words, way of life. For instance then, one test would be to see what happens to multiculturalism if you pick out farmers from several dozen cultures around the world and, I don't know, colonize them in Siberia. The results of the book quoted may have us expect a significant degree of cultural convergence that would then exert on later arrivals. Such an effect might be related to the growth of American national culture in the early period, with the limitation of massive divergence in ways of life in that context.