...except that Marx was concerned with "mere" capital while we're talking about automation, robotics, etc.. It turned out that capitalism on its own did not create the social unrest Marx predicted (at least in societies which didn't already suck for other reasons), but it may be that automating the workers out of being able to earn even a subsistence might in fact do so.
Another way of looking at it is that while Marx identified a real problem, his solution was essentially a bunch of wishful thinking which, when pitted against free market economics did rather poorly. But, free market economics is all about managing scarcity; automation points the way to a post-scarcity society (at least post-material-scarcity). Free market economics doesn't have anything to say about how to handle this -- so we're all in the dark.
It seems to me that as the marginal value of material goods diminishes relative to say the marginal value of not being beaten and robbed we should see a natural progression towards some kind of redistribution of wealth -- driven as much by enlightened self-interest as anything. ("We'll pay you welfare as long as you keep taking your contraceptive pills...")
Marx also treated capital as a way to control the means of production. One could argue that with automation, especially software automation, controlling the means of production is possible without a significant amount of capital.
Seems to me we're already seeing the natural progression you described in your last paragraph - basic income initiatives. This really looks to me like the anti-segregation movement from the 60s - a radical idea at the time, then 50 years later people don't understand how it was possible to have a society without it.
You may be right. Certainly the gay rights movement has succeeded beyond my wildest hopes or expectations during a period of generally right-wing dominance amd stalemate (the democrats have only had two years to pass legislation since 2000), and now it looks like the war on drugs might collapse. We seem to be enjoying one or two tectonic shifts in politics every decade right now. Amazing times.
I'm not from the U.S., so as an outsider it seems to me socialism, which is the prominent political stance in some parts of Europe and a respectable opposition stance in others, was/is constantly demonized there, similarly to how gay people were demonized decades ago ("recruiting" young children etc.).
So a not-unreasonable guess as to "what's next" might be socialism, regardless of whether we're post-scarcity or not, and regardless of the success of basic income initiatives. Maybe ACA will be considered the first sign 50 years from now...