Last year around this time they were working an update and it took months. There were 13 betas maybe more.
The update sucked for me. Made everything worse.
Moral of story: updates can be a bad thing. 10.9.2 actually is usable so I wouldn't want them to make things worse which history suggests they might.
According to the chart that I linked, you're referring to 10.8.3 update, which took 161 days from the release of 10.8.2.
Sadly, it makes sense. With the annual release cycle, they have to move majority of the team to work on the 10.10 now to get it in developer's hands by June/July.