However OS X gets its names, they've got about two more major variants left, Cougar and Lynx, before the nature preserve goes barren. Even before then, it's a strange scheme, as pointed out by one MacRumors poster.
… Cougar, panther, puma and mountain lion are basically the same animal. And that animal is not that big in size. So, a mountain lion is actually a smaller animal than a lion. It's like they're downgrading the king of the jungle to a smaller cat. … After Mountain Lion, if Apple still wants to release 10.9, they are going to have to use either Cougar or Catamount, which is still the same animal as panther, puma and mountain lion.
Windows can't make up its mind (Surprise!)
For an established corporation that sells the world's most popular desktop operating system to the biggest companies in the world, Microsoft's naming schemes are, honestly, kind of nuts.
It started simply enough, with Windows 1.0, 2.0, then 3.0 and 3.1, with an important side venture into Windows NT, intended for networked business clients. Then Windows ventured from its deep blues roots into the pop market, so to speak, with Windows 95, the OS originally named Windows 4.0 that launched with huge fanfare, ads featuring the Rolling Stones' "Start Me Up", and lots of bugs. There was once a Windows 96 on the drawing board that was majorly focused around Internet Explorer 4.0, but they nixed the update, and stopped the late 1990s browser wars from getting even more heated. Then Windows 98, Windows 98 SE, and Windows ME, or Millenium Edition, arrived in fairly quick succession, but each of these, as later explained, was an increment on the original Windows 4.0/95: 4.0.1998, 4.10.2222, and 4.90.3000, respectively.
Meanwhile, Windows NT was marching along, but by the time it was time for Windows NT 5.0, Microsoft switched directions and went with Windows 2000, and switched the end-user client version from "Workstation" to "Professional." If you're a professional type looking to grab a computer system that will let you run Office and jump on the new-fangled web, which one do you need: Windows 98 SE or Windows 2000 Professional? It was going to get worse with Windows ".NET 2001," but Microsoft instead pressed all their software lines into Windows XP (named for the improved user experience). But XP couldn't take the weight, and it exploded into eight different variants: Embedded, Media Center, Tablet Edition, and the now-standard bevy of "editions": Home, Professional, Business, and so on.
Currently, we're at Windows version 6.1, but that version is called Windows 7. And Windows 8? That's version 6.2. Microsoft's Windows team says that's due in large part to minimizing compatibility problems with apps. But really it shows that Microsoft has a very specific system for naming new releases of Windows and other software: somebody thinks of a name, somebody is afraid to tell that person "No," and then it goes on a box.