There has been speculation, fan art, chest hair and other shenanigans, concerning this seemingly popular character, amongst the fans at BioWare's forum. It can now be told, that Varric will be voiced by Brian Bloom who some people might remember as Leske or Dwyn from Dragon Age: Origins. This was confirmed by BioWare's very own Mary Kirby, who is also responsible for the writing of this character. The source of this information can be found on BioWare's official forum here.
More information about Dragon Age 2 can be found here.