While no release date has been confirmed Canon Rumors
is reporting with "certainty" that C-Log is coming to the 5D IV. They're also reporting that the update might not be just a simple firmware update but might require a trip to your authorized Canon service center. We'll keep you posted on dates and links for updates and/or instructions as soon as their available.
You might be asking; what is c-long and why should I care? If you currently shoot video or would like to start it's an important feature. In tricky lighting situations you may find yourself compromising by over or under exposing certain parts of your scene/subject. You could shoot in RAW with the hope of grading in post. But RAW will gobble up space and making editing a horrific task. With C-Log you're conserving space, retaining a lot of information, that can be later graded in post production to offer something that, while isn't perfect, is workable.