Fr. Z reports that the next encyclical is ready:

According Il Sole 24 Ore the Holy Father’s second encyclical is ready.
The new document is said to be called Spe salvi, “Saved through hope” (cf. Romans 8:24).  Apparently there is still a debate about the document’s title.

It could be released before Christmas, in fact around the first Sunday of Advent.
The encyclical will focus on the theological virtue of hope.  Remember that the first encyclical was about charity.
The Pope worked on the encyclical during the summer.  The translations are being prepared.