In the long term, Deepfake won't make people believe in fake videos, it will just make all confidence in video evidence disappear.
People will trust some fake videos until they see stunningly realistic videos of themselves hanging out with Hitler, or whatever.
Later we will have some video devices that use some kind of encryption and network connectivity to validate frames of video faster than they could be post-processed, creating trustworthy video. However, crazy people will just say the organizations running the validation are illegitimate.