20-Year Prospect
Barring unexpected nuclear holocaust or scientists genetically modifying grass to stop growing at exactly one-and-a-quarter inches, chances are people will still be playing golf, and the courses they play at will still need to look impeccable.
Minimum wage will have gone up (hopefully) and new models of power tools will be on the market. If anything, things are looking good for greenskeepers in twenty years. Just so long as the robots don't take your job. "What robots?" you may ask. It turns out a new study suggests some tin can with delusions of grandeur might take your place within twenty years (source).
But, on the plus side, you probably won't want to keep this job for twenty years anyway.