Paolo Rodari at Palazzo Apostolico has this (my translation)
From good and reliable Vatican sources it has come to be known today that the long-awaited social encyclical which many, including Renato Raffaele Card. Martino, had predicted would come out in December, has been shleved pro tempore. [for the time being]
The text, in fact, does not take into sufficient account the present financial storm.. Sure, then, it will not come out in 2008 and it will with difficulty see the light of day in the first months of 2009.
Whew! I am actually rather pleased.