Start of beta WOW Legion
It is on the twitch chain blizzard that Ion Hazzikostas (Head World of Warcraft) and Jesse Cox announced in live the opening of the closed beta of the extension Legion May 12 at 23h (remember, the official release of this extension is scheduled for August 30, 2016). During the live, they also took the opportunity to explain a bit more about some of their choices, as well as some of their points of views. The opening of this beta will therefore lead to the closure of the alpha version and therefore the removal of all the characters that have been created.
To recruit new testers, a "wave" of mail invitations will be performed. Make sure to check your mail, who knows, you may be lucky enough to discover the contents of the 6th expansion to World of Warcraft in exclusive (ie some content will not be accessible even for beta testers, as some cinematics of legion's history, and also cinematics about the demon hunters' history).
For latecomers, it is still possible to pre-order World of Warcraft legion.