20-Year Prospect
Emergency management will never go by the wayside. For starters, Mother Nature will always do her thing—hurricanes, tornados, earthquakes, and floods, to name just a few. And one of the hot debates of the day is global warming and the worsening conditions it'll bring.
Add to that the necessity to prepare for man-made disasters, such as terrorist attacks, bioterrorism (think anthrax in the mail) (source), and whatever else will pop up in the future. The need for experienced planners and responders is only going to grow. The Bureau of Labor statistics seems to agree, estimating job growth in this area to be eight percent between 2012 and 2022 (source).
Even better than job security, though, is job variety. Unlike many other jobs, you won't be doing the same thing for twenty years. The more experience you gain, the more you can move up into cool new stuff. You might start out generating reports and putting together emergency kits, but sooner or later you'll be the shot-caller and have more irons in the fire than a blacksmith.