European and Asian money will keep the high-demand city markets afloat for a surprisingly long time. Even if the prices stop going up and the ultra high-end properties take a nosedive, there isn't going to be much of a decrease in New York or San Francisco.
But look out in the areas where those Europeans and Asians don't want to live...paradoxically, places like Houston, Kansas City, and Memphis are going to take a much harder hit than anyone realizes, even if prices haven't gone up as much as they have in the high-demand areas.
For an investor, just hold cash for a while and wait until the high-demand markets cool off a bit and offer better opportunites. Rural real estate is a lousy investment, but OK if you just want a place to live.
Houston, KC and Memphis are not rural areas. They are still big city urban. If you want rural areas look at towns less that 10,000 people (preferably less than 2000) and at least 90 minutes from any city.