I'm not on the "they are returning slavery" rhetoric fully, yet. But the idea that this is unimaginable is also being ignorant of where some of these people are at mentally.
I'm not going to do a firehose of information, but I will give you hints on how to go down the rabbit hole. This combination anti-democratic, unrestrained capitalism, and desire for authoritarianism has its basis among this new class of rich elites, such as Silicon Valley venture capitalists. The most prominent at the moment being Peter Theil who helped bankroll Trump to a small degree and who is bankrolling Vivek Ramaswamy. Thiel has an infamous story of where he was confronted by a fellow black student during the height of protests of apartheid in the US for his rumored support of the regime and he pretty much just kept repeating that "Apartheid was a good economic system" and people who know Thiel describe him as being incapable of expressing any sort of empathy for other human beings and inhumanely cold when it comes to more humane ideas like human rights. To him, the role of government is not to care about human rights, just how much it can help facilitate the gain of capital, for people such as him.
He has funded and also found a lot of common ground when it comes to philosophy with a computer scientist by the name of Curtis Yarvin. I've had the (dis)pleasure of reading a lot of his writings and he has a sincere belief that blacks are better enslaved and they simply can't function in modern society if they are given the same rights as other races. He sincerely believes this and preaches it. It's not just hateful rhetoric, to him. It's the logical "natural order". He along with a dude called Nick Land are thought of as originators of "neo-reactionism" and "dark enlightenment" which is a white supremacist philosophy that the current political climate has taken a lot of cues from. Steve Bannon has said himself he enjoys Yarvin work and he is tied to one of the biggest republican money men at the moment. He is most infamously known for stating "some races are better suited for slavery than others" and that slavery is a natural institution.
He is also obsessed with the Scottish white supremacist philosopher from the 19th century, Thomas Carlyle who commonly argued that blacks naturally belong as slaves and quotes him on this point often.
Everything I mentioned can be found sourced here.
Curtis Guy Yarvin (born 1973), also known by the pen name Mencius Moldbug, is an American political theorist, blogger[1] and software developer.[2] Yarvi...
encyclopedia.pub
These are the individuals on the far right who carry a lot of weight, and as you can see they don't view slavery as something that is forever in the dustbin of history. In fact, it's probably a mistake in their mind we ever got rid of it. So, don't know if they "will bring back slavery" but understand there are a lot of these people who don't think slavery was a moral failing. Failing to enslave their perceived inferiors is the failing in their mind.