Since Panther also can refer to many species of big cat born with all-black coloring, Apple clearly isn’t slavishly devoted to just using actual species names. So the fact that Cougar just is the common name for the genus Puma won’t stop Apple from using it. What are they going to do in three or four years when plans for OS X 10.8 are announced? Sure, they could throw Ocelot or Lynx into the mix, even though those aren’t big cats, but that just postpones the problem a few years, until 10.10.
Who wants to upgrade from OS X 10.7 Lion to OS X 10.8 Buffalo or Camel? Nobody. And OS X 10.9 Bornean Clouded Leopard just doesn’t roll off of the tongue like Panther. If Apple needs more animals once they’re done with the cats, Bear, Wolf, or even Fox seem the most likely. The hyena is the next closest relative to the cats, but hyenas aren’t the most positively regarded animals (and mainstream society certainly isn’t prepared for an operating system named after a species where the female has a penis).
Since lions are the kings of the animal world in popular culture, my bet is that (if they stick to the cats) Lion will be the code name for the end-all, be-all version of OS X – the one that will be followed by a new operating system from Apple that makes the shift from OS 9 to OS X look like a minor point release.
Hopefully this issue will teach Steve Jobs and Apple a valuable lesson that every software project should take to heart: Don’t settle on a closed set of code-names that will only last you about ten years, even if they sound really cool. Maybe they could take a page out of Microsoft’s book, and use a combination of years (you’ll never run out of new, cool-sounding years, I promise) and random, cool-sounding two-letter combinations.