We've had two people write in telling us that the EOS 7D Mark III is currently scheduled to be announced in March of 2018.
Specifications are scarce, but both sources did claim it will definitely shoot 4K and will come with C-Log. We've known (or assumed) that 4K was coming in the EOS 7D Mark III, but this is the first time we've heard C-Log mentioned as well.
One of the sources also mentioned “first time sensor technology in a Canon DSLR”. We're not sure what that is, but it sounds like some marketing speak for the moment.
With the NAB show in April, a March announcement for a DSLR with some higher end video features does make some sense.
Take this with a grain of salt, as it comes from unknown places. As always, we hope to confirm some of these details soon.