Time for an update!
The reason why Canon still hasn't publicly announce the 25p firmware for 1D C is that they found a serious defect in the initial release (version 1.1.9 in early May), their official word is "image tearing can sometimes occur during recording". So they stopped updating cameras with this version and delayed the announcement to end-of-May (as of writing). Currently they are still working on revised version and further delay could be possible.
1D C owners, please be patient