The 7D shoots 18 MP RAW files at 8 fps with dual Digic 4. If the Digic 5 is indeed 17 times faster and the 1D X has dual Digic 5 plus Digic 4 for metering, why can't it handle RAW at 14 fps? That's not even twice as fast at moving data as the 7D, unless it turns out to be foveon type sensor or something.
It's a good question. To get the 14 fps the press release stated the mirror would stay up but still the sensor is being exposed at 14 fps and converting to jpg is additional processing after the RAW exposure and ADC so why not allow RAW at 14 fps with the mirror up? The answer then could be that data throughput to memory is still the bottleneck?
Also, the press release didn't mention of how many frames at 12 fps the camera can capture before the buffer is full.