to begin with, why "grey swan"? no doubt, it's a reference to Taleb's book. but what exactly do they mean? that what's happening in China is not completely foreseeable, but more foreseeable than the blackest of black swans?
let's simplify things -- if we define growth as growth in wealth, and examine if the chinese are able to pull off creating something like 10% more wealth every year than we did last year. there are two variables to this: how many people are working this year than last, and how productive are they.
I don't have time to research on this, but I am guessing workforce size reduction if it happens is going to be more than offset by China simply copying mature technologies from the West and increase the productivity of its people, as it has been doing. the wild card is projects like centrally planned bridge to no where, which looks productive but doesn't actually create things people want, i.e. wealth. But China has always (i.e. last 60 years) been a centrally planned economy, assuming the leadership doesn't all of a sudden get a lot more stupid, and given that the portion of the economy that's centrally planned is shrinking every year, I think one can even make an argument of putting on a few basis points of growth simply from the gov't playing a smaller role in the economy than before. (now of course the big stimulus package might completely skew the balance for these couple of years, but it's temporary noise that probably wouldn't reverse the trend.)
and argument of how big a village needs to be before it can be called a town is irrelevant.