20-Year Prospect
Despite the advent of online shopping, people will still be buying goods and services at brick-and-mortar stores in the next twenty years. So long as people are shopping in person, there will be mystery shoppers out there evaluating the experience.
There is a slight chance that as surveillance becomes more affordable and better quality, there will be a slight decline, but that decline will be negligible at best.
The need to police people's treatment of customers and behavior, as well as the quality of food or a service, will always be important. The great thing about this position is that it's a strictly human experience. Robots aren't going to be able to pass as real customers anytime soon. People may end up using a google-glass like device to make note-taking unnecessary eventually, but that's about as far as things are likely to change.