Blizzard made an announcement that because of the stuffup with Blizzcon tickets, they would release 3,000 more through a lottery system. The only condition is that if you managed at all to get even one ticket last week, you are not eligible to enter the lottery to have a chance to claim any more tickets.
Source: Zarhym. He also responds again three posts down from his initial response.
Gaiwyn of Proudmoore