Smartphones were a big deal before the iPhone. People would talk about how they were addicted to checking email on their “crackberries.” But they were niche. You could see that they were going to be big, but they weren’t there yet. Then the iPhone catapulted smartphones from a popular niche to a ubiquitous product.
Before the iPhone, they did the same thing with portable music players. Afterwards, it was the same story for tables and smart watches, although not with the same degree of ubiquity. Arguably it was the same for PCs (“personal computers,” not IBM-compatible machines, of course) and GUIs, way back when.
What big upcoming thing would they do this with now? As you say, there really isn’t anything. Maybe VR/AR, but that isn’t even in the “popular niche” stage yet, the technology isn’t there yet, and it’s far from certain that it will ever be more than a tiny niche. Otherwise, what? Self-driving cars? That’s not a new market, that’s a product feature in an existing large, mature market. AI? That’s also looking like a feature rather than a new product category.