An FCC filing released today shows that a slightly smaller Apple TV is in the pipeline.
The device, model no. A1469, is smaller than the current-generation Apple TV. It clocks in as a 93.78 mm square, and the current Apple TV is 98 mm. MacRumors noted yesterday that the latest Apple TV software update included code names, which are most likely associated with this new model. Apple filed the paperwork with the FCC in December 2012.
The third-generation Apple TV was released on March 7, 2012, so the time is right for it to be refreshed.