In New York, it isn't "affordable housing" unless it is made such under a government program, so it can be allocated in the way government often allocates things — politically. Elsewhere, however, something else is going on. Among other things, "affordable housing" developments are running into financial trouble because housing is getting too affordable, even in places like Boston where the bubble made housing unaffordable not long ago. In other places, the unaffordable units are now cheaper than the affordable units.
As a result of the bust, Boston, San Diego etc. are getting affordable, and if NYC doesn't have as great a bust, we are going to lose people and jobs to more affordable locales. Particularly young people without the insider connections to get the special "affordable" units. So stop worrying about falling real estate prices, since for all but those looking to cash out, soaring prices are worse. And New York City isn't Detroit. All those new housing units and foreclosed units will sell or rent, if the price is affordable and legal limbo doesn't keep them empty. I only hope the builders had enough of a profit cushion to keep building even if they need to price low enough that someone could actually afford their developments.