Even if you have a crash, a built road is still there and a built office still exists. Pudong is empty because the offices are expensive and it's not really in town - if a crash happens that forces the government to reconsider whom they want to target pudong at, then there will be enough people moving in there when the prices are right.
China is not developed, it's developing. It's not borrowing from the future - the U.S is borrowing from the future and giving it to china. China is taking the money and building infrastructure.
Property is not expensive in china. There is no excessive inflation or speculation. China has the typical bubble of any rapidly growing economy, but the huge internal market, massive infrastructure development, and large population of highly educated people, and the introduction of chinese businessmen to secondary markets in Africa and South America mean that the fundamentals of the chinese economy are fine. If there is any bubble, it will blow over and growth will continue.