...except that ARM laptops and desktops are the next wave, as ARM dominates mobile devices and tablets already, it's sneaking up on Linus from behind.

Additionally, Linux is the server platform, abstracting the ISA to a large degree, particularly with regards to what most people consider web applications development, tooling, etc. Docker and Kubernetes serves as this paper for many, as well.

This all will matter in the coming rise of Risc-V devices, as this ISA begins to eat parts of the ARM empire.

Linus would know a thing or two about challenging X86 (transmeta) and this probably shows in his display of his emotional wounds. I don't think his fear holds for all time nor in the coming decade.