They'll have a fully employed and aging work force making 1st world wages? Hahahaha, tell that to the 600,000,000 working for less then 20 CENTS per hour and the 1,000,000,000 (three times our whole population plus) who live in abject poverty in the country side hoping to get one of those "high-paying" jobs.
What can you really conclude about China? Most of the people who live there are agrarian, using third world farming methods, and surviving with govt subsidies. You can think of them as a huge Taiwan surrounded by 20 Laos's. Not necessarily the inevitable powerhouse you're imagining.