According to Mac Rumors, Jordan Hubbard Apple's Director of Engineering of Unix Technologies has seemingly revealed a possible launch period for the next operating system from Apple.
Speaking at LISA '08 Hubbard showed a slide during his presentation, about the evolution of Mac OS X from large servers to embedded platforms, which showed a slightly more specific date for the release of Mac OS X Snow Leopard than we've seen before.
The slide which can be viewed in a PDF of Hubbard's presentation states that Snow Leopard will see a release in Q1 2009.
Snow Leopard was announced at WWDC 2008 and at the time Apple said that the latest OS would ship "in about a year."
It should be noted that previous releases of Mac OS X have gone through extensive testing in the developer community and so far Snow Leopard has only had two test release, both of which were to a limited amount of developers.