I guess what I'm really asking (given the original subject of the post being declining Mac sales) is who is going to buy it? You can buy a Chromebook with a 13" IPS touchscreen that looks better than the Air for $250. The air is a decent machine for doing dev work, but compared to what its competitors it is a complete rip-off. Its only selling point is running OS X.
I mean, that's the strongest decision when evaluating a new machine for me. If someone wants to replace my machine, they also need to replace the software on the machine, and I don't think the Chromebook is even aimed in the same direction as Mac OS X. It doesn't have the breadth of software, hardware, or even file interaction necessary to get through the classes I took in college, let alone my self education.
If you know exactly what you need from your machine, the chromebook may very well be sufficient. I don't think you can depend on it as a general purpose computer quite yet.
Well what do most people (not just devs) like about macbooks? I would say build quality, "it just works" (macOS), and status as an apple product. The entry level macbook air still has those things. As for the chromebook comparison, macbooks have always been more expensive than its competitors at the same spec level, so this is nothing new.
I feel like saying it isn't a viable machine because of old specs isn't necessarily true since people will still buy it.