The date of sales will be May 21st at 10AM PDT, and on May 25th at 7PM PDT, both of which have the normal tickets on sale for $175 USD.
Additionally, on May 28th at 10AM PDT, they will be selling a $500 USD ticket that also includes a benefit dinner that supports the Childrens Hostpital of Orange County that will be held on the 20th of October, the day before the conventions events. This will include people being able to chat with developers, executives, and other blizzard employees.
In previous years, the tickets have gone quite quickly, so if you're planning on going you need to be ready to buy them almost instantly according to blizzards website.
For those that are not able to make it in person to BlizzCon, then you are able to purchase a virtual ticket for about $40 USD that will give you access to either a multi-channel online stream from anywhere in the world or view the events via Direct TV in the United States.
Links
http://us.battle.net - Battle.net's WoW Blog Post
http://us.blizzard.com/ - Blizzcon Official Website