You quite sure about that? The version of Windows that runs on ARM was called
Windows RT. The two versions are distinct and different architectures and couldn't run Intel x86 code for obvious reasons.
Emulating the x86 architecture in ARM would be a painfully obvious thing for Apple to avoid for performance reasons so I always thought that if they created a version of MacOS to run on ARM chips they'd be for the lower end of the market and would exclusively run apps signed from a nominal ARM Mac App Store.
I saw the
Gatekeeper function on modern versions of MacOS as the starter for that technology.
Ideally, we'd be considering a cheap 12.9" 'Mac' laptop with iPad Pro 2 and A10X Fusion as the base hardware in 2017 and perhaps coming during the lifetime of Sierra say, in March, when we might expect a refresh of iPads. This laptop would sit beneath the Retina Macbook and might be a device that comes with Cellular connectivity built in to set it apart from the Retina Macbook. The CPU benchmarks might suggest it can keep up with a Macbook Pro from 2012 but we need to see what the GPU can do in an iPad Pro.
In other commentary, the Mac Mini could not go AppleTV sized unless Apple were going to use flash storage only (dispensing with the 2.5" hard drive) and have people pay for additional space through iCloud's storage management facilities (Desktop and Document) introduced via MacOS Sierra (although, obviously, there are snafus for advanced users as with many iCloud 'features'). It doesn't make for a 'cheap' computer but should be fast performing I guess.
Although it's a candidate for light media serving duty we'd really need to see versions of FCPX and Logic Pro X for any new device to show that it's usable as a computer.