I don't think that there will be such a thing as a "robot sweatshop", because a sweatshop implies that you use people, or at least conscious beings.
While I'm sure we'll be very advanced on the domain of AI in the next few decades, consciousness seems to be a very difficult goal to achieve in such a short time. And even if we manage to achieve it, and become able to give consciousness to machines : why would we give it to robots in factory?
The question of consciousness is an interesting one. If the machine can perfectly fake it has consciousness or emotions how can we tell it's not conscious? conversely, how do we know other humans are conscious and not just "pretending"?
While I'm sure we'll be very advanced on the domain of AI in the next few decades, consciousness seems to be a very difficult goal to achieve in such a short time. And even if we manage to achieve it, and become able to give consciousness to machines : why would we give it to robots in factory?