Suppose, hypothetically, that we really do reach a stage where we have a small number of highly productive individuals and a large number of unskilled people without manufacturing work to do.
In that case, it is likely that the skilled will hire the unskilled as servants, making the skilled people even more productive (every hour spent doing laundry is an hour spent not designing the latest iPhone). People will probably also work fewer hours, and take productivity gains in the form of leisure rather than money.
If there's ever a situation where the majority of Americans are working as mere servants for the wealthy, I think simply taking the wealthy's money and redistributing it will be the more likely outcome, and that's if it's done peacefully. A situation like India's, where there's such huge income inequality that there's strongly differentiated classes, between the servants and the people who have lots of servants, isn't sustainable. People are only willing to protect the prerogatives of the wealthy if they think that overall the system is reasonably fair, supports opportunity and income mobility, has benefits trickle down substantially to everyone, etc.
In that case, it is likely that the skilled will hire the unskilled as servants, making the skilled people even more productive (every hour spent doing laundry is an hour spent not designing the latest iPhone). People will probably also work fewer hours, and take productivity gains in the form of leisure rather than money.