A mass suicide. Capitalists committing suicide for lack of slave labor force.
Possibly. It's interesting to look at the historical progression. When society was more agrarian and agriculturally based, population density was low and the wealthy and powerful could rule with impunity. Industrialism changed that, as society slowly became more urbanized, and people were concentrated in cities with higher densities. That's when national leaders and governments had to become more savvy, bringing reforms and improvements in living standards to the local populations (or sometimes just the capital city), while sticking it to those further away and less of a chance of resisting.
The Western liberal democracies were most successful at this. France, Britain, and the U.S. started favoring more liberal reforms: Expansion of voting rights, support of labor unions, social security, more help for the aged and disabled, etc. Other European countries also went along a similar path. This is what led to the capitalism we see in the West, of the kind that so many flag-wavers brag about and cite it as clear evidence that the capitalist system is so much more superior to any other systems.
But while all these reforms were taking place, what were these liberal democracies actually doing around the world? How could they manage to be able to afford and provide a better life for the home folks? The French and British had control of large chunks of Africa and Asia. The U.S. held Latin America under hegemony and ruled it with an iron fist, and we also held the Philippines and heavily pushed for the Open Door policy in China (the fallout of which we're still dealing with today). Within America, there was class and racial stratification which also worked well for the capitalists and made many people wealthy. Those of a certain ethnicity or the wrong skin color might have been vulnerable to exploitation.
So, even if they had to play the liberal game with U.S. domestic politics (which was also paralleled in Western Europe), the capitalists still had an entire world they could exploit, so giving away some "free stuff" to the hoi polloi was a small price to pay. In America, it engendered a strong sense of patriotism and loyalty which would certainly come in handy later on.
The thing about capitalists is that they're so greedy and power-hungry that they will invariably end up fighting each other sooner or later. Just like Don Corleone and Don Barzini could never really agree or get along, such has been the case with multiple nations throughout the world. In Europe, France, Germany, and Britain had a falling out and couldn't seem to make any kind of deal to coexist with each other peacefully. Germany was ultimately defeated, while France and Britain were extremely depleted and ended up losing their empires and being beholden to the United States - which they've always chafed against, but they also know, deep down, that it could have been a lot worse.
Since WW2, the great game has shifted away from outright conquest and open colonization to a more subtle approach where the West would keep up the pretense of a "free world" of sovereign, independent nations, while still trying to find ways of exerting our will upon them and making them congruent with Western interests. Kind of like what was done in Latin America, by backing some local strongman and sending in the Marines if and when needed. The Soviet Union and the ideological threat of socialism tended to gum up the works for the West in that regard, but on the other hand, it also provided a perfect pretext for using force to carry out the imperialist agenda.
After the fall of the USSR and the apparent pacification of China (heh), the Western leadership became even more reckless, ostensibly believing "there's no one left who can stop us now!" But along the same lines, we've seen a rise in the number of countries and political factions who are getting increasingly fed up with this crap. They're tired of all the BS, and they're not going to take it anymore.
I don't think it's going to be an ideological battle between socialism and capitalism. There may be some of that at work, but it may take on a different form, particularly when looking at one of the early points made in the article above:
Many government leaders see this as a matter of national urgency. They worry about shrinking workforces, slowing economic growth and underfunded pensions; and the vitality of a society with ever-fewer children. Smaller populations come with diminished global clout, raising questions in the U.S., China and Russia about their long-term standings as superpowers.
Are they worried about the world and humanity as a whole (which they should be, if they favor a global economy), or are they just worried about "diminished global clout" that comes with having a small population? "Diminished global clout" is more of a nationalistic concern, not strictly a capitalistic concern (although it can be if one's bread and butter depends upon the divisions among nations).
I remember back in the 90s, the big thing after the end of the Cold War was a "world without borders," kind of like a world-wide version of the EU. People wanted a global economy and free trade. No more wars, just one big capitalist planet where people compete fairly in an open marketplace, with no violence or any other scourges of the state to worry about. I remember talking to people who would present it that way, even if it did seem too idealistic at the time (which it was).
But the reality now is that, there's nowhere left to exploit. The global capitalist system has reached a plateau and a kind of "dead end." While we've been trying to avoid general war due to its political inexpedience, we still seem to be wary of unsettling events overseas (and sometimes even at home).
Capitalists are somewhat predictable in that they usually want to keep what they have. This means they'll invest in whatever government or faction seems most likely to be able to make that a reality.