Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
There's a thread here that says "Tomorrow". Even though it's a month old it will be 100% accurate one day. :D
 
My guess right now is that Apple does not want to have sustaining engineering working on 10.8.3 AND open up 10.9 at the same time. Therefore, announcing 10.9 is on hold until 10.8.3 is good and ready. Also, 10.8.3 is taking as long as it is because it's likely to be the final update for Mountain Lion - remember, the last one always takes the longest due to the sheer number of bug fixes.
 
My guess right now is that Apple does not want to have sustaining engineering working on 10.8.3 AND open up 10.9 at the same time. Therefore, announcing 10.9 is on hold until 10.8.3 is good and ready. Also, 10.8.3 is taking as long as it is because it's likely to be the final update for Mountain Lion - remember, the last one always takes the longest due to the sheer number of bug fixes.

I second that. 10.8.3 AND 10.9 are for what reason ever behind schedule - at least when compared with the release dates of 10.7.3 and 10.8 last year.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.