Blizzard is notorious for not announcing release dates or patch days until the very last minute -- if at all. Sites like WoW.com and MMO-Champion have had to develop relationships with people in the know in order to have any idea when a patch is coming out, and even then we usually don't find out for sure until about 12 hours before a patch makes it onto the live servers.
Not all MMORPG companies are so secretive however.
CCP, which runs the hard core space based MMO EVE Online recently had to push back an announced patch -- from Wednesday to Thursday.
What happened when they did this? Fans rejoiced that a bug was being fixed. They cheered because you finally could shoot stuff that was 0 meters away with turrets.
Now in Blizzard's world, at least the one they display to everyone outside of their organization, pushing back an announced patch would be the end of world. Cats and dogs would live together, and fire with the occasional brimstone would rain down upon the Earth. They have said many times that the reason they don't want to announce patch dates is because if they don't hit their target, they are going to upset the fans.