My intuition tells me humans will always have needs that AI can't fulfill. If AI does more and more jobs, cheaper, faster, and better than humans, then the price of these services and goods are going to drop, and that means people will have more disposable income to spend on other services and goods that are more expensive because AI can't produce those (yet).
Imagine a breakthrough not only in AI but also robotics, allowing restaurants to replace the entire staff (chefs, cooks, waiters, etc) with AI-powered robots. Then I believe that higher-end restaurants will STILL be employing humans, as it will be perceived as more expensive, more sophisticated, therefore worth a premium price. What if robot cooks cook better and faster than human cooks? Then higher-end restaurants will probably have human cooks supervising robot cooks to correct their occasional errors, thereby still providing a service superior to cheaper restaurants using robot cooks only.