TeamLiquid has apparently translated a post from a Korean website which claims that "according to the game developers," Blizzard will announce Starcraft 2 at Blizzard's World Wide Invitational (WWI) to be held in South Korea. If you've paid any attention to Korea and Starcraft you'll know it's no joke over there. Our "hardcore" gets air quotes compared to Korea's hardcore, which should actually have just been written in all caps, bolded and italicized. Although we have absolutely no idea about the legitimacy of this Starcraft 2 information, we do know that there is a megaton announcement planned around May 19.
Speaking with Joystiq, Blizzard wouldn't confirm Starcraft 2, but said they are planning on making a huge announcement at the WWI. Starcraft 2 had previously been hinted by Blizzard's VP of business development. Obviously announcing Starcraft 2 in Korea is only appropriate, as matches are held in stadiums, carried on television and are practically a national sport. This way, Blizzard can announce the next WoW expansion at min-E3 and then save the Diablo 3 announcement for BlizzCon. So if sometime around May 19 you suddenly feel a disturbance in the force and millions of people screaming, that's just South Korea imploding from the news that Starcraft 2 is coming.