It won’t happen. (Really).
A limited number of social orders are possible: i) genetically imperial (Han Chinese, Russian Empire), ii) large hierarchy of casts (india), iii) small homogenous and dynamic (europe, japan). iv) tyrannical hetero-tribal, v) failed peoples that cannot hold territory (diasporic unlanded people).
Every experience with heterogeneity has failed. (Middle East, Brazil, and most obviously, India.)
The most successful states are homogenous kin groups (China, Korea, Japan, the nordics, and until recently western europe.)
The Chinese/Japanese/Korean civilization will very soon dominate the world economic and political sphere, and their racial exclusion will be copied by the rest of the world.
The problem isn’t racism. The problem is that most unsuccessful races, subraces, tribes, and clans, consist of excessively large underclasses whose standards of living cannot be satisfied now that the advantages of western technology have been redistributed.
Look at brazil. Look at the USA. The ‘whites’ are trying to separate. The jews remain separated. The diasporic chinese separate. It’s underclass peoples that commingle.
The optimum social order is homogenous, for the simple reason that we redistribute to kin and resist redistribution to competitors.
The optimum possible social and political order is kinship. (Do the research)
Kin selection is an evolutionary advantage. (Do the research)
The experiment with Democracy has largely failed. (Do the research)