This is a great idea for the public good, but unfortunately there just isn't much economic imperative for the camera companies to invest in it. Security-sensitive filmmakers and journalists represent a vanishingly small niche, not a meaningful market. For the rest of users, photos taken on stand-alone cameras are generally meant to be shared, not strongly protected, meaning encryption is at best a "nice to have" not a "need to have" or perhaps even a "want to have". And that means that if it comes at the price of even a tiny degree of inconvenience, consumers will refuse it.

Having said that, it's not inconceivable that camera makers can solve this problem (a) cheaply and (b) in a way that is "off by default" for most consumers but available if needed. But I'm not holding my breath.

I think it's far more likely that we'll see the quality of phone photo/video quality become "good enough" for security-sensitive users to abandon standalone cameras entirely than that we'll see camera encryption catch up in the other direction.