I've got a feeling this won't have anything to do with the Mac computers.
Probably either a video iPod, or something along those lines like the streaming video airport.
If there is anything on the Mac front, it may be a switch to the 7448 PPC G4 that was introduced by FreeScale in June. That would replace the 7457 currently being used.
The 7448 is a 90nm part vs the 130nm 7457, officially goes up to 1.7Ghz at launch (7457 only goes to 1.3Ghz 'officially'), and only consumes 10W at 1Ghz. That is actually a significant improvement in terms of power over the 7457 that is currently used in iBooks, PowerBooks, and the eMac. The 7448 also has a 200Mhz FSB vs the 7457's 166Mhz FSB, 1MB L3 cache vs 512k L3 cache, and improvements in the execution pipeline and AltiVec. It would extend battery life while increasing performance and probably reliability (less heat).
Here's hoping, anyway.