AI in knowledge work will probably see the sort of changes people talk about - jobs destroyed but new jobs created. A robot that can do cleaning, construction, even retail sales - that's going to wipe out swathes of jobs. You'll have armies of workers that can work nonstop, don't steal, don't want raises, don't have a bad day at work, and can be retrained as quickly as you can install new software.
I don't see that there's any reason we won't be able to have those kinds of robots in, conservatively, 20 years, and I don't see how we get close to replacing the number of jobs they take.