There have been several reports of tech related sites discovering visitors using OS X 10.9 in their analytics reports. While we haven’t seen it show up in our reports, 9to5mac, AppleInsider, CultofMac and others have.
We know this can easily be faked but it’s hard to rule out the fact that Apple may be in testing phases of a new OS X development. For the past few years, Apple has been releasing a new version of OS X on a yearly basis. OS X 10.8 Mountain Lion was just released in July, OS X 10.7 Lion in July of 2011, OS X 10.6 Snow Leopard in August 2009.
At this rate, expect to see a new unnamed OS X from Apple in mid 2013. If they continue the cat named theme, it’s uncertain what the next name could be as they are running out of options.