Real photojournalism will demand cryptographicly signed image provenance.

That's not enough. Movies use set design and wardrobe and practical effects to fake a bunch of stuff in camera.

A camera that can attest "this is what I saw" doesn't really extend that attestation to "and what I saw was real."

Physical film has to be scanned

Uh, what? You can both reproduce, enlarge and project film photographs without them ever touching a digital device.