Why Apple Is Quietly Rewriting iOS in a Language You've Never Heard Of

Apple spent a lot of effort adapting or creating languages, starting with Clascal/Object Pascal (or Woz' SWEET16 as an alternative high-level assembler-like intermediate language and 16-bit virtual machine) over Objective C (bought from Brad Cox and Tom Love and significantly extended/changed over the years) to Swift. They also used these languages to implement critical parts of the system software, e.g. for the Lisa or the NeXTstep ObjC-based driver framework.

So this speculation has quite some credibility - but, as the author states, I think this is still in an early stage and will take quite some time to become mature.

There are other people designing their own system-level language and OS, e.g. Drew DeVaults Hare and the Helios microkernel and Bunnix Unix clone based on Hare - this is a single person effort, so given Apple's resources, this is definitely feasible.