First, it's good to remember that demographics have a life of their own. That's not good from the point of view of those of us of European descent. We're only 10% of world population and falling rapidly. Worse, it seems we're responsible for all the world's problems and therefore aren't very popular.
In Europe, I expect the '20s will have a lot of mass migration, the largest in scale since the barbarian invasions of the fifth century. This time there will be millions, then tens of millions, of Africans coming across the Mediterranean, looking for a higher standard of living—like all migrants.
In the United States there will be hundreds of thousands coming up from Central America. A Reconquista movement will develop, to make the Southwest Hispanic again. And young Chicanos and cholos won't be interested in paying 50% of their incomes to support old white broads on Social Security in New England.