I can´t understand Canon. They bring up a big update for the 7D, but the necessary errors in the 1D X and 5D Mark III are not fixed until yet. Also a lot of wished functions for the 1D X and 5D Mark III are not included until yet. Canon you loose.
If the firmware update for the 7D is able to speed the camera up, it´s no problem to speed the 5D Mark III up. But nothing happens.
The 1Dx and 5D3 have been out 5 minutes, the 7D has been out 3 years. That suggests the opposite of 'no problem'. Also different camera architecture (different generation processors, different chip read off)
It seems from canons own blurb that it was work done on the 1d series that was transposed in this fw upgrade to the 7D.