We're looking to stay closer to a more realistic experience with CK3 for the time being, so there's no overtly supernatural content in the pipeline.
That said, there are plenty of really impressive mods out there that do an amazing job of adding their own supernatural mechanics to the game. Way of Kings and Princes of Darkness are two really good total conversions built around supernatural mechanics, while Witchcraft and Highlander Immortals both add good supernatural mechanics to the existing setting.