I think this way of thinking is distracted. No type of media has ever been a source of truth in itself. Videos have been edited convincingly for a long time, and people can lie about their context or cut them in a way that flips their meaning.

Text is the easiest media to lie on, you can freely just make stuff up as you go, yet we don't say "we cannot trust written text anymore".

Well yeah duh, you can trust no type of media just because it is formatted in a certain way. We arrive at the truth by using multiple sources and judging the sources' track records of the past. AI is not going to change how sourcing works. It might be easier to fool people who have no media literacy, but those people have always been a problem for society.