There are zillions more cat names left. And I doubt Apple would care if two different cat names were synonyms for the same species. And even if Apple did run out of actual cat species names, there are plenty of non-joke cat names they could use, such as griffin.
http://en.wikipedia.org/wiki/Feline
Wildcat
Ocelot
Lynx
Bobcat
And given that Apple did Leopard and then Snow Leopard it means that they can also do Bengal Tiger, White Tiger, Siberian Tiger, etc.
In other words, there's no shortage of big cat names left. And Apple is gonna do way more than another 3 versions of OS X anyway, I don't know where you got that number from. After OS 10.9 comes OS 10.10, the numbers don't stop at a single place.
Yeah but Bengal/Siberian should have been updates to 10.4 then calling 10.7 (or whatever) "Siberian Tiger" would confuse the hell out of people.