Does x86 maintain any real advantages over ARM at this point, other than the ability to run legacy software? I'm genuinely asking; all I know is that ARM devices can be really powerful these days and they're also much more power efficient.
In many cases dramatically so (and I say this as someone who doesn't even like x86 much). It depends on your application. For small embedded applications where things like BOM or electrical power massively dominate, neither x86 or ARM is worth it (and this is in a world where you can get a small ARM for less than a dollar -- we're talking about CPUs that cost pennies in volume). For pretty much every "mobile" applica…
There's a push for networking chips (ones with built-in multi-gigabit NICs): Mellanox Bluefield, NXP Layerscape [the one that's in the new SolidRun workstation!]..
And for regular old server chips (or "cloud" in marketing speak): Ampere eMAG, Amazon Graviton..