With the rename from OS X to macOS, should the tag be renamed too?
Only the newer versions will be called macOS, the older ones will still be called OS X Cat-of-choice. I would propose to go with a synonom instead of a renaming.
Today (June 2016), the synonym points macos -> osx so that we can decide at a later date to flip things around. If there is an answer that makes a strong argument for never merging the two, we might want to undo the synonym so that the macos questions are distinct.
Just like that, all 16.5k osx questions are now macos questions! With what I presume was a chat between moderators outside of this meta question, bmike has reversed the synonym, such that osx → macos. Enjoy the shiny new badges!
Also, since this change occurred quite suddenly, it seems like no-one thought about the tag wiki and of course it's now disappeared. I've updated the tag wiki of macos based on the prior tag wiki.
I think that osx is a decent tag for the most part. osx refers to the modern version(s) of Apple's Operating System, which is titled as OS X. Earlier versions, before the 'OS X' line started (named after the big cats), were simply named Mac OS <insert version name and number here> - 'X' was added after Mac OS version 9. As such, I would think that the tag, macos would refer to legacy Apple Computer software, instead of newer software. Nonetheless, I would welcome the new tag! :)