It would seem a new piece of DLC for Dishonored called "The Other Side of the Coin" is coming. A list of trophies over at PS3trophies.org would certainly seem to suggest so.
Here's a list of trophies that point to a substantial bit of DLC:
Just Business - You got the information needed from the Rothwild Slaughterhouse
Missing Pieces - You obtained Delilah Copperspoon's identity from Thalia Timish
Well Connected - You purchased all of the Favors in The Other Side of the Coin
No Regrets - You completed The Other Side of the Coin in High Chaos
Redemptive Path - You completed The Other Side of the Coin in Low Chaos
Whisper Ways - You completed The Other Side of the Coin without alerting anyone
Cleaner Hands - You completed The Other Side of the Coin without killing anyone
Rats and Ashes - You caused a death using an arc mine and a rat
Message from the Empress - You performed a drop assassination from atop the Empress statue
Stone Cold Heart - You spoke with the statue of Delilah in Timsh's estate