That's really not as far away as you seem to imply.

Just look at the difference between current politics and forty years ago. If politics changes as much to the extremes in the next 40 years, you get your genuinely bad government in far less than 40 years.

Add in the known tendency of humans globally to take refuge in extremism and racism in a recession, well, one more deep recession could do it.

The US 40 years ago was a relatively backward, sexist, racist, and homophobic. Politics has gotten an order of magnitude better since then, and the people are greatly more virtuous. If we get a similar change in the next 40 years we'll be living in an amazing society.

Look up "regression to the mean" ... :)

And to believe a strong statement like "an order of magnitude better" I'm going to need some stronger evidence. For a hand-wave I'll be willing to agree with "not much worse, if you look from the right angle of perspective". In case you hadn't noticed, but you got a misogynist hateful clown running for president that's currently blocking my view of this supposed order of magnitude betterment. And there's crowds cheering him on. It's an order of magnitude improvement like dada was to classicism--entirely orthogonal.

I largely agree with you, but what do you think changed? Biologically we haven't changed since much darker ages. That leaves culture, and culture is inherently consensus-driven.

What happens when the consensus breaks down?

We've changed massively - that was the point. Who's to say the next 40 years is the same direction?

Also many things have improved, but certainly not everything.