If you want to go to BlizzCon in October, you have one last window to buy your tickets: 8:00 p.m. PDT tonight. That's 11:00 p.m. Eastern, and 10:00 p.m. Central. This news comes from an announcement on the main page of the WoW website. The announcement further tells us that all the available tickets were sold out within minutes of the Blizzard Store coming on-line this afternoon.
Considering there will be a third hall open this year, we believe around 12,000 tickets have been made available (this number has also been reportedly confirmed by phone sales reps), which is 50% more than the 8,000 that were sold last year. The World Wide Invitational that took place in June also sold out very quickly.
In the case of the WWI, additional tickets were made available after the primary batch had sold out. However, and this is important, there is no indication Blizzard will do this again.
We'll update with any further information when we have it.