Sorry to disagree with most here, but honestly I just see this as an evolution for the film industry. Just take a couple of Start Wars scenes for example - final scene of the original, they didn't hire a thousand extras to stand there in the the throne room, they hired a hundred, and simply used matte paintings for all the rest. Podracing scene in Phantom Menace the tens of thousands of spectators in the stands weren't hired extras, they were q-tips packed into a scale model. AI extras are just the next step in VFX.
Now don't get me wrong - I challenge anyone not to feel gutted at the story of Phil Tippett, and how his legendary stop-motion skills were made redundant almost overnight on Jurassic Park when the production team decided that computer animation was now "good enough" to create the dinosaurs, but that's the world we live in.
Are we now just a few more years away from being to tell an AI to "create me a 3-hour historical epic based on the journeys of Aeneas after the fall of Troy"? Very likely
Will most of us be amazed when watching such an AI creation? Very unlikely at the moment, but in 10 - 20 years? Maybe it will be hard to tell such a creation from the very best writing and acting of today. Maybe that will lead to the demise of studios completely - you'll just create your own content on demand. But very probably even if that does occur, many people will still want human written and acted content.
Just like the stop-motion animators, and a huge number of legacy IT skills that many of us are very familiar with, maybe many of the current roles in film and tv are destined to become niche in the future - still needed, no less worthy than they are now, and indeed maybe very highly in demand (and paid accordingly), but over time fewer people will retain them and other newer opportunities will arise.
Sorry, but that's just life...