It's done when the publishers say it is.
1UP.com has an interesting feature up called "Delay of Game," which examines game titles that were canceled or delayed and looks at what happened. Several of the titles on the list are MMOGs that you were probably looking forward to at one point.
Blizzard's, Valve's, and id's ability to answer press and publishers' "When?" with "When it's done" is hard-won; unless you've launched a WarCraft or Half-Life, you don't shirk deadlines -- you commit to a date and cross your fingers. We've collected some of the most famous (and infamous) cases of PC game delays, botched launches, and outright cancellations, along with the unfortunate, serendipitous, or sometimes downright bizarre causes.
Read more at 1UP.com.