20-Year Prospect
With robots encroaching on virtually every field, you'll be in one of the few lucky ones that stays mostly human. Sure, the more modernized boats become, the more robots will be capable of handling certain functions with new technology. At the end of the day, though, the spontaneity and skill required for a successful voyage is best left in the human hands of the sailors.
Of course, the job outlook for merchant sailors is directly related to the health of the economy. The more freight that needs to be shipped, the more sailors will be needed to deliver it. What way will the pendulum of the economy be swinging twenty years from now? Trade in your compass for a crystal ball to get that answer, but it probably won't be too far off from where it is today.