[allenbrunson]

From Apple's perspective, the whole point of the work they put into macOS is to add value to macs, the selling of which is their bread and butter. (or used to be ... i guess now it's mostly selling iPhones.) If they were to open-source it, it would be quickly modified to run on bog-standard PCs, removing Apple's motivation to put any more effort into it.

In other words: don't hold your breath.