More Ratchet & Clank confirmed for 2009
According to this 1UP story, the end of Ratchet & Clank: Quest for Booty contains confirmation that a new game in the series is on the way for next year.
Upon completion, the title shows a splash screen saying, "The quest continues in Fall 2009..."
There's a picture of it through there, and everything. Quest for Booty's out later this month.