As long as there is less housing being built in existing upper income urban areas or new higher end housing in nearby ones than there is demand for such housing, gentrification is inevitable. The upper income people displace the upper middle class, the upper middle class create new upper middle class housing by displacing the middle class, the middle income folks displace the poor who are screwed. Nimbyism and knee-jerk anti-development feelings among upper middle class liberals help speed up the process. Go to San Francisco - the whole damn city is turning into one big gentrified area. New York is far bigger relative to its metro area so there are limits on how far this can go, but Manhattan - same thing.

Brownstones in my Brooklyn neighborhood went for $100K fifteen years ago, now it's $1.5M and that's not just the housing bubble but a fundamental shift in the economic class of those who live here. The new residents oppose building more housing, piously saying that it will gentrify the area even more. Somehow they don't see the irony. Not to mention the fact that the bad side of gentrification is not the fact that a neighbourhood gets upper middle class residents but that the poor are forced out. Not building new housing decreases the influx of better off people to a given neigbourhood while accelerating the displacement of the poor in both that area and in other ones (some of the would be residents of new housing go to other areas). Yeah, I'm ranting, but it pisses me off.