OS X 11.0 does not necessarily follow 10.9 - they could easily go to 10.10.0. From the Keynote it does not sound like they plan on naming it OS XI any time soon.
Good to point out — IIRC, they didn't refer to it as 10.9 in the keynote, just Sea Lion and Mavericks (the first being a joke, the second unfortunately was not). So they may keep calling it OS X for future upgrades as well.
I understand the PR motivations behind the new name (even though you may have heard our money is hiding in Ireland and elsewhere, we're still a true blue American company!), but I agree with people who say that most people are going to wonder "What's that?!" A very small number of people will know what it is, and it's not catchy.
It is possible to use obscure names effectively — look at Google. Who even remembers now that it was based off a mathematical term (googol)? No one cares because Google sounds catchy and cool. Mavericks? No one knows what it's referring to, and it's not catchy at all. A handful of people who are surfers in the Bay area may identify with the term — what about everyone else? If they weren't going for catchy, then something else sea-related that would be more universal, or at least more identifiable California/American name would have been better IMO.
Tom Cruise killed the name in 1986 and the John McCain and Sarah Palin dug up its corpse, **** on it and buried it again in 2008. The end.
Sarah Palin is the first thing I thought of when they announced the name (starts at 0:20 below).
Maybe that's part of the reason I have a negative reaction to the name Mavericks? Hopefully the OS will be good enough that people won't care about the name.