I think we are putting too much emphasis on emulation. Apple's switch to ARM on the Mac is already well underway, and most of the "emulation" has been replaced with a direct development environment that is both happy and profitable.
That environment is called "iOS".
Keep in mind that I am not talking about UI, here. Rather, I am talking about the development of native ARM code that is happening amongst most major applications. Microsoft, Adobe, etc. are already on board with ARM code for their major applications, (you can bank on them knowing where Apple is headed, and it isn't toward Intel's roadmap). Office (not the full suite, mind you, but a good chunk of it) is already running on ARM, and so is a good chunk of Adobe's stuff, including the full-blown desktop version of Photoshop (due later this year), new 3D modeling tools, etc. In fact, all of the world's most popular apps are already running on ARM.
In the not too distant past, when Apple switched from OS 9 to OS X, Microsoft and Adobe were conveniently absent from the game, waiting patiently to see if Apple could pull off the transition. And, again, when Apple switched from PowerPC to x86, MS Office and Adobe CS were absent. As were almost everyone else. Apple had to spend a ton of R&D money developing emulation environments, and then wait patiently as their partners drug their heals.
This time around, Apple has quietly used the iPhone and iPad as experimental development environments in which they have drug their partners forward kicking and profitably screaming. Thus, most of the development work has already been done. When they switch to ARM there will be no emulator—Marzipan will see to that. Apps will just work. Yes, some developers (Adobe and Microsoft included) will have to work on the UI, but much of the necessary code will have already been laid.
Also, the iPad Pro is the experimental Ax platform that Apple is using to provide developers with top of the line ARM chips that offer performance at least at or near the low/middle end of x86. This does several things. First, it gives developers a look at high-end ARM systems; second, it provides a profitable medium for software development and experimentation; third, with Marzipan (upcoming) it offers developers a way to reach every customer Apple has, regardless of the platform.
Basically, when Apple pushes the Mac OS-on-ARM button, the software will already be there with no need for emulation. iPad Pro's powerful architecture will see to that. Apple has very carefully lured their entire developer network into the next major transition, most of them unknowingly. Office is [mostly] ready; Adobe CS is [mostly] ready; games and social media apps are [mostly] ready.
The next transition will be [mostly] seamless, and entirely free of any emulation environment, because developers will have already done the legwork. Does this mean MacOS apps will be awesome? No, not at all. Some will suck (many suck right now). However, I do not think we have seen anything close to the beginning. A few experimental apps (Home, Stocks, etc.) do not make the system. They are only laying out the framework.
As far as high-end systems are concerned, I am guessing Apple will solve the issue simply by chucking lots of cheap Ax cores at the problem.
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