Blizzard Entertainment President, Mike Morhaime, has confirmed that Starcraft II is delayed because of the Battle.net 2.0 component is not ready yet.
The expected release date for Starcraft II: Wings of Libery, is now the first half of 2010 according to Morhaime. We have included the press release featuring BOB KOTICK and MIKE

While Starcraft fans are waiting and hopeing for a Starcraft 2 release this year, an analyst from from Sterne Agee states that this might not be possible.
As a result of the delay on sci-fi first person shooter Singularity from Activision, the analyst thinks that Starcraft 2 is going to be a 2010 title.

Update: Blizzard has commented on the speculations whether Starcraft 2 has been delayed or not.
 

In an interview with Eurogamer, the vice president of game design at Blizzard Entertainment, Rob Pardo, has revealed that World of Warcraft held up Starcraft II's development in about a year, because the staff was called off to work on World of Warcraft.
The development of Starcraft II started already in 2003, and Blizzard has had a playable multiplayer version since 2005.

While all Starcraft 2 fans are waiting on the beta phase to begin, Dustin Browder, lead designer on StarCraft II, has said that the playable beta will run for about "four to six months", according to kotaku.com.

With that said, the chances for a Starcraft 2 release in Q4 this year, is fading.