Cheap/slave labor isn't the only reason companies went to China. There's EPA regulations, OSHA regulations, union labor demands, burocratic red tape, high taxes, etc.,etc.
They might leave China but I doubt many come back here
In 9 years there I saw no slave labor.
Did have unscrupulous contractors that worked those who came in off of the rice fields without permits and wouldn’t pay them, not totally unlike some contractors here.