Multicultural Citizenship and New Migrations

Through offering a normative conceptualisation of a national case, Britain, I ask what is the relationship between the post-immigration normative project of accommodating citizens-marked-by-origin and the managing of current flows of migrations and mobilities?
While multiculturalism requires reconceiving citizenship and shared identities, it has assumed that a collectivity of citizens in the form of a state/polity has the right and the capacity to control immigration and that migrants want to be and should be accepted as citizens.
But what if the nature of immigration (and other relevant circumstances) change such that difference is no longer so salient an issue, citizenship no longer seems to be so normatively prized by migrants; and immigration is less amenable to control?
Does multiculturalism still have traction in these new circumstances? British multiculturalism was developed in a context of immigration control and does not challenge the right of the state to control immigration, while insisting that it must not be exercised in ways that are discriminatory or stigmatising in relation to the composite and overlapping criteria of race, ethnicity and religion that are at the heart of post-immigration British multiculturalism. While a cosmopolitan version of multiculturalism is also present in Britain and is largely compatible with a more political, communitarian national multiculturalism, the two seem to have incompatible views on national identity concerns and so on immigration control. This is seriously problematic for progressive politics today but a solution is not clear.