Look at the iPhone SE. For customers who prefer a compact form-factor at a low price point, Apple still make a phone with the body of an iPhone 5 and the guts of an iPhone 6s. It's a niche product, but an important part of the line-up. "Old chassis, new internals" is a standard part of the Apple playbook. Mac sales represent an almost irrelevant part of Apple's revenues, but they're a vital part of the overall Apple ecosystem.

Apple still have the tooling for the 2015 Macbook Pro. The NRE costs to put a modern processor in that chassis would be relatively modes, because it's a much larger chassis with a more straightforward thermal design. The market for such a machine might not be large, but it's extremely important for the health of their ecosystem, because developers developers developers.

Personally, I think that the post-Jobs Apple has developed a nasty case of cargo cultism. Obsessive focus on the user experience has transmuted into obsessive focus on arbitrary design goals - thinner, lighter, fewer ports. They're making record profits thanks to the huge margins on iPhones and the strong vendor lock-in on iOS, but they're burning the goodwill that kept them alive during the lean years. If Apple can't find a way to delight customers rather than frustrate them, they're facing a serious long-term problem.