ARM just makes sense for portable devices for obvious reasons, x86 isn't dying though. For the average person who needs a laptop to do some professional-managerial work ARM is perfect.
ARM is more efficient and as a "system on chip" reduces the need for as many other components on the boards, phones for example. Unless you're doing heavy cpu or gpu intensive tasks there's a bunch of upsides and no downsides to ARM.
That's my impression as well. I'm confused about the “just”. There's many non-portable devices that don't have too heavy workloads and that I'd think would benefit from better energy efficiency.
Oh yeah the article is about the laptop market, but of course all sort of non-portable devices run on non-x86 platform. I'd even say x86 is the minority unless you reduce it to just desktop workstations.
There is also a sizable market for laptops that do not do much more than log onto a remote desktop. Especially with remote working, that has becomes the perfect middle ground between security, cost, and ease of use. A cheap ARM processor would work perfectly for those machines.