I think the key think that always seems to be ignored is that the these consumer devices such as iPhone, iPad, Watch, would not of been so successful, and simply cannot succeed going forward, unless there is a quality software ecosystem to power them.
What do developers need to write this software on? Macs! Macs are an integral part in the success of pretty much every Apple product, their continued development is essential to the success of Apple. Developers of all kinds have flocked to the Mac over the last few years due to OS X and great computers such as the MBP, so much so that at pretty much every conference, the vast majority of users in the audience flaunt glowing apple's from the backs of their lappys.
The idea of programming on an iPad is ludicrous. Maybe it's OK for simplistic stuff, but without the power of Unix under the covers, support for multiple displays, proper multi-tasking, mouse support, an abundance of developer tools, it's never going to work for real development.
I sincerely hope that this unprecedented delay in the introduction of new macs is a sign that some big improvements are coming to the mac lineup, and not just some weak component delay excuses. If not, we could see more and more developers being tempted back to Windows or Linux purely because better computers exist for those platforms. We can already see this trend happening in the high end graphics, video, and other pro spaces. The lack of a new Mac Pro for nearly 3 years has seen many pros move back to Windows based workstations purely because they can get their work down faster on newer machines, even at the cost of leaving their beloved OS X behind.