There was also the 68K transition to PowerPC a long time ago. And more recently, the 32-bit to 64-bit transition.
And for a lot of the older Mac developers, iOS was kind of like another migration. And iOS has gone from armv6 to armv7 to arm64, plus the x86 and x86-64 simulator targets. Not to mention that there is now an LLVM Bitcode requirement for Apple TV and watchOS.
Apple and its developer community has a lot of experience with architecture migration. Each transition built on the experience of the previous and got smoother each time. Apple has been very good insulating their frameworks and tools from the architecture, and the Apple developer community has gotten very good at following Apple's guidelines to minimize disruption since there have been so many of these transitions.
Forgot to add that I think the real thing keeping Mac on Intel is the bullet point that Intel Macs can install Windows.
In the PowerPC days, Apple had trouble convincing people to switch to Mac because Windows being so dominant, everybody was afraid they might need Windows for something and that would make a PowerPC Mac an expensive mistake. The Intel switch alleviated many fears because in the worst case and Mac OS didn't work out, they could just install Windows. Bootcamp and virtualization provided additional options.
Apple has always seen Mac and iOS as different markets. Mac is still a small market compared to Windows. They are still trying to grow which means still trying to convince Windows users to switch and the safety net of Intel is still useful. (Windows RT isn't a realistic option.) I personally haven't seen iPhone users wishing for a big laptop or desktop that runs their same apps.
Windows was already on ARM with Windows RT, for which I believe Microsoft did the work of porting UEFI and standardised bridge (PCI) technologies to ARM.
While speculating: Apple could conspire with Microsoft to standardise these technologies together to lock up their ecosystems against the Linux / Android monster :-)
The hard part for Microsoft is not the porting of Windows to ARM. The hard part has been and continues to be convincing existing Windows developers to port their apps to UWP.
The reason Windows on Mac is useful to people is because people have may programs that do not have acceptable equivalents on Mac OS. These apps are usually legacy programs that probably fill special niches, and the cost of "modernizing" is usually not justified. This effort would be required to port these apps to Windows ARM, which last time around also required porting to UWP which Microsoft is still pushing, but not easy to actually do for a lot of code bases.
A new Microsoft irony kicks in here is that if they are successful in convincing the huge Windows ecosystem to migrate to UWP away from Win32, et. al, they may actually kill their lock-in advantage. A serious rewrite at this stage may also invite Mac, Linux, iOS, Android ports. In this case, Apple no longer needs to care about Intel Windows and this bullet point becomes less compelling and maybe they could reconsider.
You can use the new Centennial technology to wrap an old Win32 application as an UWP Store app. If the app was made with .NET it might even run on ARM.
I think this market is getting smaller and smaller year over year (I no data to back this up unfortunately). They could honestly build a MacBook with ARM in the near future while keeping the pros around with x86 for a while longer. They could reduce the price by hundreds of dollars switching off of Intel processors which would undercut a huge amount of competition.
The sole reason I can use a Mac for my paid work is, that I can run Windows and x86-Linux VMs, as I need to run Intel based software on those operation systems.
Well yes and no. I ran Windows in VirtualPC (I think) on a PowerPC MBP for a while. Pretty slow but good enough for Outlook, Word etc that I needed the compatibility for.
Say, does anyone know who owns the IP for FX!32 nowadays?
Putting aside the fact that Windows RT was a commercial failure and discontinued which makes it weird to push yet another effort that this would be anything more than some niche demo thing like Raspberry Pi support, Windows in of itself is not what concerned potential Mac switchers.
People are concerned that they have some mission-critical, unreplaceable app that only runs on Windows, that has no acceptable Mac analog (doesn't exist, doesn't have feature parity, data formats are incompatible).
Windows on ARM doesn't solve anything because almost no Windows apps that people care about were ever ported to Windows RT. (It was probably more likely there was a Mac port.)
And for a lot of the older Mac developers, iOS was kind of like another migration. And iOS has gone from armv6 to armv7 to arm64, plus the x86 and x86-64 simulator targets. Not to mention that there is now an LLVM Bitcode requirement for Apple TV and watchOS.
Apple and its developer community has a lot of experience with architecture migration. Each transition built on the experience of the previous and got smoother each time. Apple has been very good insulating their frameworks and tools from the architecture, and the Apple developer community has gotten very good at following Apple's guidelines to minimize disruption since there have been so many of these transitions.