I agree that wage stratification has already occurred, but I think AI will do nothing to make it worse than tech already did. It will do nothing to replace service workers or laborers. Again, it's only a threat to managers and decision makers.
Many of the middle income jobs in the U.S seem vulnerable to automation. Professions like truck drivers, longshoreman and radiology techs that provide compensation between 40K and 70K could probably be mostly or completely automated in less than the span of a generation.