NOTE: I am a putting on my futurist hat, and making predictions based on current trends. I do not want these ideas to happen. GDP is evil and capitalism will fail…
There is a trending opinipon and totally due to the racism of Donald Trump: the only good immigrants are white.
Combine that with the requirement that capitalist societies need never-ending growth (as measured by the GDP), and we have western nations with low fertility rates relying on immigrants to boost the GDP…
And we get to a point, whether spoken out loud or barelun disguised, that western countries will start fighting over the available white immigrants. And that creates some crazy scenarios!
Bidding war – white migrants might be offered incentives to move to a particular country. As each country tries to outdo the others, we will find out what such an immigrant is “worth”. Especially if they have skills and/or a lot of money.
Not allowed to leave – if a population numbers emergency is declared, citizens might not be allowed to move to another country. Then we have the ackward scenrario where tourists might defect!
Rampant breeding – in poorer white countries, people might churn out babies, not just because of massive government incentives, but actually wishing that some of their kids will move to another country and send back the riches.
State breeding – if citizens are unwilling to make enough babies, the state might pay donors and surrogates, and create babies that will be state-owned and operated. And then placed in a foster care system.
The shortage of white people to welcome to your land will inevitably lead to decisions on what is the next best. Christianity is likely to be a key factor, and so people from strongly Christian countries could be welcome. Asians as well, especially the paler kind. Chinese quite possibly, if they are allowed to leave. If they do, they could become the consumers China needs, while also sending money home.
The winner, the last (western) survivor of capitalism, will be the country that inspires their population to have many more kids, goes hard early to import the very best migrants at any cost, and keeps their country a desirable place to live, by all measures. And they start ASAP!