I'm not saying it's a good idea, but we are talking about Apple allowing IOS apps run natively on Macs. iOS apps are already running natively on macOS - but only if you have Xcode. Apple could really just include the x86 based iOS framework that it already has in the next version of macOS and tell developers if you want to run on Macs, just modify your UI to support a third target - you are already probably targeting iPhone and iPad - let Xcode bundle the x86 build its already doing while you're testing.

As far as Intel based phones, that's even easier, tell developers they are realeasing an x86 based phone in the next year, either you bundle an x86 version - again you're already testing an x86 build every time you run the emulator - or you'll lose compatibility. Apple has never been afraid to abandon apps when it transistioned processors.

The Android situation is different, if people have a choice between buying an Android device that is 70 percent compatible and one that is 100% compatible. The one that is 70 percent compatible is at a disadvantage. But if people want an iOS device and Apple switches to Intel and they lose some apps what choice do they have?