Raven had layoffs in August 2009 after the completion of X-Men Origins: Wolverine and Wolftenstein, explaining that the studio had "slightly [reduced] its workforce to better reflect the studio's upcoming slate."
nope Activision has issued the following statement: "With the recent completion of Singularity, Raven Software is realigning its workforce to better reflect the studioâ€™s upcoming slate." Raven Software does not currently have a game announced, but it was rumored in May that the studio was being tasked with working on Call of Duty: Black Ops map packs for DLC.
Kotaku's source claims that the studio will be focusing on downloadable content and has been reduced to a single team. It's doubtful that Raven will be making DLC for any of its previous titles at this point.
It is easy to speculate what is going on within Activision's Call of Duty division, but there are just too many possibilities following the collapse of Infinity Ward. Presumably, Modern Warfare 3 would have been released in fall 2011, but the status of that project is unclear.
Looking at the information here, it is possible that Treyarch would be tasked with assisting on the completion of Modern Warfare 3 with what remains of Infinity Ward, while Raven Software handles post-release DLC for Black Ops. Activision probably doesn't want to miss a holiday season without a new Call of Duty on store shelves.