Ignoring the tools that developers and creatives use to create and sustain this thriving ecosystem is a very dangerous move on Apple's part. Skylake chips for the Macbook lines have been available for months and the Mac Pro hasn't been updated since 2013. OS X itself continues a long list of bugs and this only grows with "customer" features inevitably introduced down the line. El Capitan was supposed to give Apple a year to slow down and fix things but we have found it has been a huge problem in our work environment.
Datacenters don't run on iPads stacked in a rack, media companies don't play stuff out of an iPhone with a dongle. Xcode alone is the single reason OS X is still incredibly relevant. I don't see Jony Ive designing the latest iOS devices on an iPad for years to come and ignoring these professionals is not a good move.
Here's to WWDC, when the Skylake chips suited for the Macbook line were introduced 9 months prior.
Most of the developers I know prefer OSX because of the close-enough-to-linux terminal experience and compatibility of most libraries. Rails, Scala, Node, JAVA all run pretty similarly on local machines as they do on the servers.
I suppose it just depends which flavor of developer you hang with!
I don't know of many people working in an office environment, much less as a developer, who would be satisfied with an iPad Pro as a daily driver when it comes to getting the amount of work you can get done on something like a Macbook Air.
Perhaps I just don't understand iOS well enough. I'd love to see a video of someone actually working and multitasking effectively on an iPad at the speed that is possible on a Macbook. Most of the videos that Apple releases show work that is limited to video capture, editing and illustration.
Look at the Windows Phone. Fine device by all accounts, but it's biggest gripe from potential users is the app ecosystem -- or lack thereof. Take care of early adopters and take care of the people who keep your mini-economy running. It is short-sighted of them to fall flat in this arena. Arguably though, they've not been doing anything terribly impressive for quite some time by way of product.