20-Year Prospect
Since it's highly unlikely that our nation's murder count will ever drop to zero, you can count on having a job for, oh, forever. As long as you keep up with the rapidly evolving technology, that is.
Take the Light-weight Analyzer for Buried Remains and Decomposition Odor Recognition system, or LABRADOR. This tool could put cadaver-sniffing Fido out of a job (sorry, boy); not only can LABRADOR locate dead bodies by seeking chemicals related to decomposition, but it can also read those same chemicals to give forensic scientists an approximate date of death.
And yes—you want to be the guy who knows how to run this mechanical pooch, not the guy replaced by him.
Of course, with great power comes great responsibility. As a forensic scientist, you need to be super-duper careful about how you do your job. You don't want to follow the example of the Houston technician who was found to have engaged in improper procedure in the crime lab.
So long as you don't royally screw up like him, and so long as Minority Report stays a science-fiction story, you'll still have a job twenty years from now.