According to a post at Thisisgame.com, Blizzard will announce the sequel for StarCraft in the home land of StarCraft: South Korea. The World Wide Invitational (WWI) is a Blizzard event where top gamers are invited to play Blizzard's games, and that's where the announcement is claimed to be.
Starcraft 2!
Starcraft 2!
http://sc.gosugamers.net/news.php?id=6151