What happens if they don’t catch the next wave? In that case, they will still be wildly successful. They’ve already had the iPad, which is the clear winner in the tablet market. They’ve already had the Apple Watch, which is the clear winner in the smartwatch market. They’ve already had the AirPods, which is the clear winner in the earphone market. None of these are the one-in-a-generation products that the iPhone is, yet they are all massive successes that bring in tonnes of money.
Apple will probably never have a hit as big as the iPhone ever again… but that’s perfectly fine and not at all incompatible with massive success and huge profits.