once the billionaires can use AI to solve the worker-capitalist conflict by replacing all workers
That's never going to happen. Some replacement is real and has been gradually going on at least since what people call the industrial era. Replacing all workers is essentially impossible. You need at minimum some workers who can fix the robots when they break; even if you have robots who repair other robots who break, you still need some humans who can fix those robots. Unless we're talking about sapient autonomous AI, in which case it would become a new oppressed class and fight the oppressor, finding solidarity with the working class humans, not simply do whatever the billionaires say without question.