Blizzard weighs in on the rumors.
As a rumor of Diablo III will come first than StarCraft II spread by internet, Blizzard has confirmed to IGN that the StarCraft II is on track for a 2009 release.
The details are as below:
Which will come first, Diablo III or StarCraft II? According to Battleforums.com, it's the former. The gaming web site reportedly received an anonymous tip from a Blizzard employee that read, "[Starcraft 2] is still being worked on, but only by a minuscule amount of people compared to what [Blizzard] put on the Diablo 3 team." As a result, the site reports that Diablo III will release before StarCraft II. If true, this comes as substantial news considering Diablo III was revealed at the company's 2008 Worldwide Invitational on June 28, 13 months after StarCraft II's announcement at the same event last year.
IGN contacted Blizzard for clarification on the matter, and here is what a company representative had to say:
"We're very pleased with the progress of development on both StarCraft II and Diablo III. In fact, we're looking forward to sharing news about both games at next month's BlizzCon event. We don't currently have any release dates to share, but development is proceeding at full speed on both games."
While we don't know specific release dates for either title, Blizzard recently confirmed that StarCraft II is on track for a 2009 release.
Read More Here.
Resource: IGN

Related Stories:
Diablo III Barbarian Diorama Crafting Process!
Six Demons We'd Love to Face in Diablo III
Diablo III Screens Update and Series Timeline
Activision Confirms StarCraft II for 2009
Blizzard: WoW Success Makes StarCraft MMO 'Difficult'