We don't understand a lot about global warming yet. Some estimates indiate a 20 rise by the end of this century, others indicate it may be much sooner while other theories indicate the breakdown of some of the major ocean currents will cause an ice age.
As Infi said, you are more likely to loose value due to hurricanes, especially around the gulf coast if that is the area you are in. We are entering a natural cycle of more hurricanes which seems to last for decades, and the warmer ocean temperatures seem to be causing them to be more severe.
If you live on a coast subject to hurricanes, you basically are rolling the dice each year you remain. As hurricanes increase in number and severity I would guess values will decline. Of course, if you suffer a direct hit, not only is the value at risk, so is your well being.
So, Nebraska perhaps does sound like a good option
