I like dropping the X, but I really dislike Apple's terrible use of case. iOS is horrible enough, but tvOS, watchOS and macOS look absolutely dreadful, each a stumbling block in any sentence they appear in. Nobody with any sense of style or legibility would abuse case like that.
Not at all unlike those people who style it as 'OSnews' instead of the obviously correct and only way to style it, namely 'OSNews'. Yes, this is an internal struggle over here, and yes, this stuff matters.
It's widely expected at this point that Apple will rebrand Mac OS X to simply 'macOS' next week at WWDC, but hidden in today's announcements regarding the App Store was yet another hint at the change. In a FAQ from on the iTunes Connect website, Apple mistakenly refers to Mac OS X as 'macOS,' again prematurely hinting at the change.