According to this, Valve will release a pack containing the new TF2 map "Goldrush" within a month.
"TF2 update: you may’ve heard that new achievements, maps, and unlockable items are on the way," said the Steam update. "The first map, Goldrush, introduces a new game mode. The BLU team must escort a high-tech mining cart through a series of checkpoints to the RED base within a time limit. The more BLU players near the cart, the faster the cart moves. The cart stops if any RED team member is in the vicinity. We’re balancing the map now; look for it within the month."
TF2 playes are being a bit spoilt at the moment having only just received a CTF update to a map called "Well". Just shows how much love Valve has, we guess.