The screenshots clearly show playable Orks within the game's item-based singleplayer mode, suggesting at least an Ork campaign. The characters seen are Kaptin Bluddflagg, Mister Nailbrain, Spookums, and Brikkfist.

[Update 12:05PM] Producer Jeff Lydell explains that the campaign will not only feature Orks, but multiple playable races. "We all love the [Space Marine] Blood Ravens here at Relic Entertainment," explains Lydell in the press release. "But there are also a lot of fans of the other races and armies out there so we decided that Retribution should allow the player the freedom to experience the campaign from the perspective they select."

"As well as the single player campaign, Retribution will feature new multiplayer units, maps and an entire new playable faction" that has not been seen before in Dawn of War II, leaving the Dark Eldar, Imperial Guard, Tau, and the Necrons up for grabs.

The game will be released in March 2011 for the PC.

A trailer has also been found, which can be seen below:

[Update 12:23PM] The press release has gone out and can be found below:

WARHAMMER 40,000: DAWN OF WAR II - RETRIBUTIONTM ANNOUNCED

New multi-race expansion coming for the critically acclaimed RTS from Relic Entertainment

AGOURA HILLS, Calif. August 17, 2010 - THQ Inc. (NASDAQ: THQI) today announced that a second stand-alone expansion for its genre redefining real time strategy game, Warhammer 40,000: Dawn of War II, is scheduled for release in the first quarter of 2011.

Taking place years after the events in Dawn of War II: Chaos Rising, this title allows players to choose their perspective with the first multiple-race single player campaign in the Dawn of War II series. The first race to be revealed is the savage Orks, but no matter which race is chosen players will be taken on an epic journey through each story arc, revealing the answers to many questions left open in previous Dawn of War titles.

As well as the single player campaign, RetributionTM will feature new multiplayer units, maps and an entire new playable faction when it ships.

Jeff Lydell, Producer of Dawn of War II - Retribution commented: "We all love the Blood Ravens here at Relic Entertainment, but there are also a lot of fans of the other races and armies out there so we decided that Retribution should allow the player the freedom to experience the campaign from the perspective they select."

Warhammer 40,000: Dawn of War II - Retribution is scheduled to be released for Windows PC in the first quarter of 2011.

About Retribution

It is ten years since the events of Chaos Rising and Sub-Sector Aurelia has been in a constant state of warfare with the Imperium struggling to retain control. The apparent betrayal of the chapter by Gabriel Angelos and his Space Marines has shaken the Blood Ravens and now the Imperial forces are beset on all sides by hostile aliens. Retribution allows the player to select the race of their choosing in a battle to determine the very survival or destruction of the entire sector.