Indeed, there is a whole complex history behind this as these things are not static and change over time. Around the mid century there was a big shift in population in the US from urban to suburban which was not equally distributed across race and class lines. There were various reasons for this but certainly a major factor was the mass adoption of the automobile and the buildout of associated infrastructure.

So is a similar shift away from the urban eventually going to happen in China as high speed rail connectivity expands even into the most remote rural areas and as the buildout of general infrastructure continues? I've seen some indications that this is already happening to some degree, as digital infrastructure and the spread of e-commerce allows people to conduct economic activity without having to be physically located in urban centers.

For now it looks like the migration from rural to urban is still ongoing and overall stronger than the opposite trend, and it seems to me this will continue for a while, but eventually an inflection point may be reached.