20-Year Prospect
In spite of what Law & Order and its many offshoots would have us believe, violent crime in the United States has been decreasing. This doesn't mean you won't have a job in twenty years, however.
Why? Because here in the USA, we just love to put people in prison. There were about seven million individuals—or one out of every thirty-five American adults—in the hoosegow in 2012.
Given that the for-profit corrections industry makes billions of dollars off prisoners every year; that we throw people in jail for silly, as well as serious, offenses; and that the majority of those imprisoned hail from populations white America just doesn't care that much about, that seven-million-imprisoned figure won't be decreasing significantly anytime in the near future.
This is great for you and your job security...unless, of course, you get replaced by a robot.
True story: The South Koreans have experimented with using four-wheeled, five-foot-tall robots to detect problematic behavior in prison populations. Clearly, no one in South Korea has seen the Terminator movies.