The EOS-1D C isn't just firmware
There have been reports around the web that the upcoming Canon EOS-1D C is the exact same camera internally as the EOS-1D X (other than the PC sync port) and Canon is just charging people $7000 for different firmware.
I have spent considerable time trying to find someone at Canon to clarify the reports as well as someone to open their EOS-1D C (no one would do that for me!). The information I have received backs up what Canon said at the development announcement of the EOS-1D C, it does in fact have a different hardware configuration inside. While the DIGIC V processors, image sensor and AF module are all identical to the EOS-1D C, there is in fact “reworked circuitry and design to dissipate heat for the 4K recording”.
So is the reworking of the internals worth the additional $7K? If it's required for the 4K resolution, and the 4K performance is top notch, then I don't see why it's not. This camera is targeted to professionals and priced accordingly. Volume sales of this camera will be far lower than the EOS-1D X, which probably makes the cost of production higher.
There are a few people I know that will open the EOS-1D C when they get their hands on it, I know I will be. That's going to be the only way to 100% prove the internals are indeed different. I do wish Canon would clarify this point and put it to rest, which they may do when the camera is officially announced.