The Pyro hinted at something being revealed on Monday, and boy did she deliver.
The PyroMania update promises Meet the Pyro 'within three days', with the official timer reading at around 50 hours from the time of this post. The blog also notes three days worth of updates to be revealed once per day up until the release on Wednesday. Today's reveal is a gamemode and map called "Doomsday", which is focused around the two teams fighting over which team gets the honor of launching Poopy Joe, the space monkeynaut, into space.
Stay tuned to ValveTime and the Team Fortress blog for more updates in the days to follow.
EDIT: Valve have added a picture of a banana to the bottom of the PyroMania update page which leads to files. These files show transcripts and images of the court case intended to discuss the where-abouts of Poopy Joe. These files were previously found on Friday during the TF2 Summer ARG.