That's the problem. Nothing is next. Cell phones have peaked. There's nothing they can really add to them anymore. The real problem is the types of activities people do on cell phones don't really require anything more powerful than an iPhone 6S. It's like they keep making more advanced phones but people don't really need them to browse Facebook, Twitter, and YouTube or snap a few pics or listen to Spotify.Apple doesn't have R&D from another division to help and nobody is forward thinking enough to figure out what's next.
I said it in another thread and was scoffed at but it's a wrap for cell phones. Especially now that they aren't subsidized by the carriers. Apple will have to transition to something else.
Official Apple 9/12/18 Event Thread | iPhone XS, XS Max, XR, Apple Watch Series 4, iOS 12 & Mac OS
Apple is in some respects a dinosaur. The way they ran that smartphone side of the business worked with there was growth in the area but as time goes on smartphones have matured to the point that if you bought one 2 years ago you can probably keep it 3-4 years before actually needing to upgrade and if you but a used one from a year ago or so it's good enough.
From there the Chinese manufactures step in and make cheap lower end phones and mid range phones that are more than adequate.
Apple finds themselves raising their prices on their customer base that will continue to shrink as a result of the maturation of the market and the raised prices.
At some point and it might not be right now but something has to give or a death spiral is entered like what Cable TV faces. Apple is doing well now, maybe they transition away from smartphones leading the charge and something else becomes their bread and butter.