I like to think of what the Apple // could have become, had Jobs not killed it off. We would have surely seen development beyond the //gs.
I'd like to think that the ARM cpu would have been a logical progression, being that it was an offshoot of the 6502 used in the Acorn boxen. Not compatible, but very similar. I can imagine an early ARM-based // with a 65816 coprocessor of sorts, which could take over the bus and drop into some sort of "compatibility mode" for older 65xx-based software. Eventually I imagine it would have given way to an optional compatibility card (as we saw with the Mac LC), and finally have been replaced with cpu emulation as we see today.
The // was always a much more open architecture than the Mac, too. It makes me wonder how OS development might have diverged from the path it took. ARM Linux wasn't a thing back in the early 90s, only Intel Linux, so I imagine some other kernel would have been chosen. But the // would have had to go to preemptive multitasking and protected memory at some point. Apple at its core has always been a hardware company, so I think it's not too far out to imagine that we'd have seen some sort of movement towards 3rd party OS development, or at least 3rd-party inclusions in a more open OS than the Mac went with (though the Mac didn't get protected memory until OS10, lol). I think a plausible outcome could have been some sort of GSOS-type finder running on top of a Mach microkernel, with the ability to drop to some sort of advanced BASIC command prompt. Or perhaps Lua; I think it was around in the early 90s.
The Linux kernel would probably have been ported to ARM a little earlier, assuming that the //s-that-could-have-been were more popular than the Acorn machines globally.
And as a more open architecture than the Macs, they may have given PCs a better run for their money. Commodore failed (IMO) because of bad management, so I think the Amiga would still have disappeared. But the // would probably still be here, and probably somewhat more popular than the Mac currently is.
I'm not trying to bash the Mac or anything. They're great machines, too. I loved the PPC architecture. But my understanding is that the // was killed off by management and internal competition (Jobs-ism, heh).
For me, it's fun to think about how things might have turned out differently, and to hack together stuff that "could have been", kinda. Perhaps not interesting to the retrocomputing purist, but.... Let's call it "Speculative Computing".