I wouldn’t count on Yao Ming quitting the Chinese national team. My guess is that his product endorsements in China are worth more to him than additional years of his NBA career. The Chinese man-on-the-street view is that China made Yao Ming everything he is today. (Which is my mind is horsepoop, given that he could have done the same exact things if he had grown up here in America, but it gives you a window into the kind of warped things the Chinese believe). Not playing for the national team would reduce his value as a product endorser.
I’ve always wondered how much of his paycheck he gets to keep.