20-Year Prospect
As long as there's a public that needs 'ministrating, there will be plenty of jobs out there. The industry-wide growth projection is a whopping 14%, mostly due to all the new organizations sure to spring up (and occasionally collapse under a pile of red tape) (source). From Uncle Sam to your Uncle Sam who works in the Parks Department, public administration is a fairly stable bet as far as outlook.
That is, until the aliens finally invade. In that case, we're sure our new overlords will figure out administering us lowly humans in their own special way.