With the introduction of iCloud, and the way the OS is moving towards the cloud it would be no surprise if the OS started using birds of prey, i.e. Falcon, Hawk, Eagle, Golden Eagle, Bald Eagle, etc etc.
I could also see them just losing the animal thing all together. It was probably a nice run through with the cats that started in 2000 and they wanted to close the door with it.
I really love Lion, I don't understand why people complain so much. Yes, I've noticed a little bit of a memory leak, but I'm sure they'll fix that. And no, I couldn't ever go back to Snow Leopard.
Having said that, I could totally see them transition to bird names (which would be cool, but their implementation of cat names was just genius it gave the name a cool factor you just don't get with "Vista"). But it seems like they're ditching all that cutesy stuff that started this beautiful platform. They've scratched out the "Mac" in Mac OS X, and they no longer have the awesome intro movies that gave youtube millions of hits, all while rapidly progressing to a more streamlined experience.
Apple, the weird, fun-loving, quirky-little-think-different company is dropping all that for a professional image with simple, sleek notebooks,
today's pop-culture(think lady gaga, and all the other things the youth's are into) and boring professionalism (no more white macbook

). It's sad that they say the best days of Apple are ahead, but everything that established this brand is departing.
It's not necessarily a bad thing, I'm sure they're more great apple products to come, but I guess what I'm trying to say is that all the little things that defined them, the quirky things that made using a mac so enjoyable, so different, is happening to leave us. So no, it wouldn't surprise me if they dropped the naming all-together in favor of a more "streamlined" naming technique such as "Windows 7."
Whats next to go: Startup chime.
