Note that recent low birthrate i.e. (2) does not immediately map to shrinking real estate demands: young people born 20-30 years ago are still moving to cities, looking for a job, and a place to sleep in, hopefully with not-too-long commutes. There will still be a bunch of young couples trying to get a home and being ruined by unfinished construction like you've mentioned.
Young people in Shanghai, Beijing, Shenzhen, and Xiamen/Amoy haven't had the means for a flat since... at least 6 years ago, when the per-square-meter price broke CNY 50 K. It's been understood as "maybe my parents have some savings from the ζθΏ demolition money for the down payment" sort of deal since then.
Smaller cities are more possible though.
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Tangential: a good part of everyone's income in those big cities goes into rent and mortage, from the average worker to the restaurants and shops downstairs. It's always been screwed.
