I think you're half right -- the rise of AI will lead people to suspect that any piece of media they encounter may be fake.

Where I think you're missing a piece -- pervasive doubt in media does not lead inevitably to people becoming better at independently judging veracity of media.

For an all-too-real example, "Fake news". In the last 10-20 years, we've seen conventional media that has attempted to sew doubt in any source of authority other than itself. Millions of people were trained to doubt everything they hear from any media outlet left of Reagan.

That doubt didn't result in those people developing critical thinking or media analysis skills. They picked their "trusted source" and ignored everything else.

To be clear, I don't think the people to whom this happened are uniquely naive or stupid. Ordinary people with lives and jobs don't have time to learn media analysis just so they can filter 10% real content out of a 90% fabricated newscast. We've seen what happens -- people find the "least bad" media source and uncritically believe everything that outlet says.

Media which requires careful study to verify defeats the point of consuming media.