Apple's Director of Engineering of Unix Technologies, Jordan Hubbard, spoke at Large Installation System Administration Conference (LISA) '08 last week. LISA, co-sponsored by USENIX and Sage, generally runs six days: six days of full-day and half-day tutorial training sessions, three days of technical sessions, and two-day vendor exhibitions. LISA is targeted at engineers and system administrators and is a very in depth technical conference.
At this years conference, Hubbard held a talk about the evolution of Mac OS X from large servers to embedded platforms. You can find the presentation slides here. MacRumors picked up that one slide details OSX 10.6 and puts the release date as "Q1 2009":
It is unusual for anyone at Apple to slip up and publicly reveal product information or time lines, so we can assume this is a genuine target date for Apple. Macworld 2009, San Francisco, is due to kick off on January 5th 2009 and it is rumoured we will hear more about Snow Leopard and possibly the introduction of an updated line of Mac Pro machines, i7 maybe?
Either way it's clear Apple has to push this update out as soon as possible. Microsoft is quickly readying Windows 7 and if it's ready for Q4 2009 and Apple's OS slips then it could be an interesting battle next Summer.