..in December this year 
Source: Is Mozilla's 2011 roadmap unrealistically ambitious?

Mozilla has published an updated roadmap in which it lays out its plans for 2011. The organization hopes to significantly shorten its release cycle and deliver a total of four major releases during 2011, cranking the browser up to version 7 by the end of the year.
Source: Is Mozilla's 2011 roadmap unrealistically ambitious?