Such clickbait.

Sure the gold rush, get-rich-quick-cause-there-are-two-of-you era for mobile apps is over. But the boom for mobile apps will never be over, much like web apps will never be over. How many billion dollar websites emerged a decade after everyone said the web boom was over?

Apps are merely a distribution platform for services. As the world evolves, we will never run out of needs for services.

As long as you're solving a need and you're capable of communicating it to your target market, you will make lots of money.

Apps and software in general will forever be more efficient than their predecessors, and thus, IMHO, the app boom has only begun.