New tidbits about upcoming Canon firmware updates surfaced on the web. As you know, Canon is going to release three firmware updates, specifically for the Canon EOS 5D Mark III (price & specs), the Canon EOS-1D X (price & specs) and the Canon EOS-1D C (price & specs).
The firmware for the EOS 5D Mark III should be released by the end of April 2013. This appears to be rather sure.
The firmware for the EOS-1D X will be available in May as it was announced.
The firmware for the EOS-1D C appears to be a little bit more problematic. Canon may make an announcement by the end of April to let us know when the firmware that will deliver the 25p/4k will be released. It is said that there are some issues with the encryption of the firmware, in order to avoid hacking or reverse engineering. The rumored 120fps at 720p mode now is said not to be part of the release version of the firmware. Stability concerns are the reason.