[musicale]

Who knows, maybe Apple will upgrade sandboxing to jails/containers and add a FreeBSD-style Linux compatibility layer. Or maybe they'll go full-on MS and include a Linux kernel alongside Xnu using Hypervisor.framework. (Note that in my experience the networking design of Ubuntu on WSL broke containers that worked fine on regular Ubuntu in Virtualbox/VMware/etc., but YMMV.)

Something like that is certainly possible, though they'd have to have some reason for it, and they don't appear to at the moment.

[pjmlp]

macOS doesn't need WSL, it is already a certified UNIX.

[musicale]

Precisely - macOS already is a perfectly good native BSD that (as you note) is UNIX® certified by The Open Group.

However, linux app binaries (notably docker images, which we're talking about here) need some sort of linux runtime, compatibility layer, or VM, in order to run on macOS.

The original implementation/version of WSL was an interesting POSIX-compatibility personality/layer for the NT kernel, but Microsoft seems to have decided that running a Linux kernel in a VM provided a better user experience (and probably made it much easier to track feature parity with Linux.)