Are less and less people buying iPhones, or more and more people buying phones? (Not a rhetorical question, I don't know whose numbers to trust for mobile stuff.)

Apple's business is not one that has to own a market to make gobsmacking amounts of money. As such I doubt they see being outsold by Chromebooks as being a serious problem; they've been being outsold in the laptop market forever and are still making yachtloads of cash.