I like the idea
! Maybe not for 10.9, but for the merge between OS X and iOS, if it ever happens.
For the 10.9 name, my first choice, personally, would be the ocelot, and then the saber-toothed tiger.
For the next generation OS, whatever it will be (iOS I?), possibly naming their operating systems after land formations would sound cool (iOS I 1.0 Volcano, 1.1 Mountain, 1.2 Gorge, etc.). If they wanted to go into space, I would name them after constellations (iOS I 1.0 Andromeda, 1.1 Pegasus, 1.2 Taurus, etc.).