Agreed. People need to stop thinking about this as a change in ISA. The important part comes when Apple starts loading their silicon with custom, specialized components aimed at improving OSX.
Apple is unlikely to ever have any major SoC features which are generally useful to end users that are exclusively available in their chips for more than a year or two. Even if Win10 ARM vendors or whatever’s coming for PC are playing catch-up with Apple, we’re unlikely to see major divergence. People still need to get roughly the same things done whether they prefer Apple or otherwise.
It's not enough to have an equivalent capability - if you want a Hackintosh, you'll need to present those capabilities in a way that fools macOS into believing it's running on supported hardware. For now, ARM has been limited to the low-power desktop/mobile and high-end server niches. Apple Silicon will go for the space between as well.
OTOH, Apple is smart enough not to tightly marry its software to a given hardware architecture - they were compiling Rhapsody for Intel from day one and a lot of iOS is directly lifted from macOS. Its lineage started running on 68K, then HP-PA, SPARC, x86, then mostly PPC, then mostly x86 again, and now it'll switch to mostly ARM.
Apple's custom silicon play is not about the users.
Its about the media vendors.
Apple can afford to outright buy most of them. What I think they are doing, is preparing themselves for a time when they can own media, as well as the devices you use to view/experience it.
I don't think the Piracy wars are over, guys. They're gunning for us, and .. unless we've got tunnelling electron microscopes and other tawdry machines, its gonna be harder and harder to crack.
Hypervisor + Emulation? Unless they did some very serious obfuscation of the binaries they distribute it wouldn't be particularly difficult to guess what their new hardware did. Obviously wouldn't be as fast but it seems doable.
You'd need a computer that's substantially more powerful than a Mac in order to emulate one. I believe Apple's premium will not be high enough to make this economically viable.