We think we are already in a post truth world, but we are barely starting down the path. There are tools that can already fake anyone’s voice or face. The impact will be, as Gary Kasporov puts it, “destroing the concept of objective truth”. We have a lot further down that road to go. The future will proceed in stages:
The first scandal
A best as we know, we haven’t yet had the big fake tape. Someone will be scandlaized by something they truly didn’t say or do. It will be a messy, partisan, fight - and the first true witch hunt.
Future tapes, true or not will come out and everyone will deny them. This will be the next version of “My account was hacked”, but now it will be a plausible defense in many situations.
Authenticity of original sources
Information aggregates will need to have impeccable reputations to be trusted. The best sources will be direct, verified, authenticated channels. A celebrity or politicians own social media or website. The power of the famous will grow compared to the anonymous. The power of investigative journalists to create new shared facts will break - only the sources of interest will have that power. One exception may be live events, but eventually technology will speed up and even erode the trustworthiness of that. No politician will have to worry as much about their past.
I don’t see a way to preserve objective truth, to maintain the power of “seeing is believing”. The deniability stage will be messy and ugly, but the end result is a lack of trust and the ability to hide, deny, or obscure anything that is released by an unimpeachable source. We are in for a rough ride.