Not categorically disagreeing with you - just injecting a few notes of caution:
Windows 10 for ARM 64 bit has been a PRODUCT from Microsoft for over a YEAR now (and for 32 bit ARM back to 2016!). It handles x86 by automatically and silently Cross-Compiling the code into ARM-Native Code. Then it runs THAT. No "Emulation" Required!!! Also, An ARM-Based Mac would have an ARM Boot Camp. Boot Camp is pretty much just a set of Hardware Drivers.
True - but AFAIK you can't actually buy Windows 10 for ARM unless your name is "Dell" or "Lenovo" - that might change, but it might also be because there's no real standard ARM hardware platform or even a single "standard" ARM processor (part of the appeal of ARM is that manufacturers can pick'n'mix cores, GPUs, various codecs, vector processors and other hardware acceleration features). Intel Macs have always been, basically, PC clones built around bog-standard Intel chips, PCIe and AMD/NVIDIA GPUs. There's no
guarantee that Windows-for-ARM would be compatible with anything other than MacOS (esp. if they use proprietary A-series GPUs). Even Linux/BSD will depend on someone compiling an ARM/Mac compatible distribution and suitable hardware drivers (which will need open specifications and could be hindered by dependence on copyrighted firmware 'blobs').
Emulators/cross compilers etc. certainly have a role to play - I've used the 68k emulator on PPC, 'Classic mode' on OS X and Rosetta in my time and although they've done a great job as 'bridges', performance has
always been 'meh' - not everything is compatible and optimisations and processor-specific hardware accelerations tend to get stripped out. The result was fine for 'light' applications (MS Office wasn't really CPU-bound) but if your daily driver was, say, Photoshop with CPU-heavy plug-ins, an Intel Mac was hardly a compelling upgrade until Adobe had ported CS for Mac to Intel.
Plus, if the emulators/cross-compilers get
too good, Intel or AMD might set the lawyers on them:
https://www.theregister.co.uk/2017/06/09/intel_sends_arm_a_shot_across_bow/
Actually, I don't think backwards
I'm fairly certain that they won't do something as foolhardy as immediately commit the entire Mac line to an "off the cliff" transition like that.
Well, that's the $64,000 question: they did it with XServe (no, a Mac Pro or Mini with a rack adapter is not a substitute for a proper rackmount server with redundant PSUs and lights-out management), they did it in 2013 with the Mac Pro (by letting the cheesegrater get thoroughly out-of-date before switching to a radically different concept), they did it with the 2016 MBP (if you don't like it here's a 2-year-old entry-level rMBP at a new higher price), to a certain extent with the Mini and the Air, they're doing it
yet again with the Trashcan/Mythical Modular Mac Pro transition and, while were at it, the iMac is heading for its second birthday...
See also Apple Maps, FCPx and the Photos app - which may be OK today but were all half-baked when Apple prematurely tried to push them on users.
So, unfortunately, although I'd hope otherwise, botching the Intel/ARM transition by letting the Intel models get horribly out-of-date first would be pretty much par for the course.
Because by (say) locking down MacOS, iOS-style, so you could only install Apps from the store, Apple get a slice of all App sales and in-App purchases. As with the above - that's in Apple's hands and doesn't depend on technology.
Apple isn't a charity and
whatever they do, PCs and phones are a maturing technology that isn't going to generate the sort of growth that it used to. They'll naturally be looking for ways to force obsolescence on hardware and make more money from services.
I think this speculation is making the (allegedly) forthcoming announcement of the Mythical Modular Mac Pro interesting: will they pile a lot of investment into doing something innovative with a Xeon (in which case they'll need to support Intel for the foreseeable future) or will they come up with something courageous with 32 ARM Cores driving a shedload of Metal-optimised shaders/vector processors? The latter would be really exciting and innovative... if they already had a credible, up-to-date Mac Pro for customers who needed one three years ago.