Assuming they're conscious this would be a problem -- but most of the things we would consider "slavery" could be done with non-conscious agents. This is also true of most jobs -- they wouldn't need to be conscious and self-aware to replace most of the mundane drudgery.

It's an open question whether consciousness can be simulated (I think it's probably far, far into the future or impossible). However, a synthetic superintelligence is in the process of being created and that is something we need to start preparing for in the near term. I think that will be disruptive enough to keep everyone busy for decades.