I'd speculate that since the X thing has so much appeal to most, Apple will probably continue the roman numeral trend and go to OS XI.
OTOH good marketing practices dictate that they should totally change the name if it is a major OS release(ie lots of changes). Maybe they'll do something microslothy like "OS Pro": or, maybe the genius who named the latest iPad will have his way and they will just call it "The New OS".
Funny a friend and I talked about this the other day. I thought they would just go to OSX 11 but he said there was no reason to just keep going like 10.12 or something. When it comes down to it I think most consumers just know Lion or Snow Leopard. So if they keep up with a naming system of some type it won't matter so much what the version number is.
I believe the X in the OSX was in deference to Steve's NeXT computer line—something to do with keeping the spirit alive. If you want to keep hocking the same product for the next decade, you might as well call yourself MicroSoft. Even RIM has jumped on the X bandwagon with BB10 (conveniently skipping 8 and 9), and you know if RIM is adopting the practice, it must be really dated. Nope, they're better off to come up with some new concept no one else has come up with yet. Something less lame than "the new OS" too.
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