The evidence is mounting for an OS X name change. Once again, Apple has referenced the Mac operating system not as OS X, but as “macOS,” online at its website. This time, the reference was made in developer documentation.
It's been on the horizon for a while now, and even if online documentation hadn't previously referenced “macOS,” we'd have guessed that this change was incoming. Now, Apple has once again made reference to macOS online (via MacRumors), in developer documentation concerning its 85/15 switch for subscription revenue; as such, we're expecting a name change to be announced during Monday's WWDC keynote.
I don't see macOS bringing anything different to the platform, and I think this is going to be a superficial move more than anything else. Before now, calls for the iPad Pro to receive its own forked version of iOS have been made, and I'm in agreement: the more powerful tablet needs further differentiating factors on the software side. But at the same time, I'm not sure macOS is going to be cross-platform.
It's also not known whether Apple is going to continue naming its Mac OS releases after Californian landmarks, or if macOS is going to launch with a first iteration 1.0 release. Of course, iOS, watchOS, and tvOS releases are named by the number, each one begining with 1.0. We'll have to wait and see.
Apple since updated its website to change “macOS” to “OS X.”