1. Stagecraft/virtual production is a thing, yes, but the backgrounds are not "AI rendered," they're 3D scenes built in Unreal. They have to be, because they need to dynamically react to the camera moving to create parallax.
2. Yes, some people are using AI to plan scenes. With respect to your relative, those people are not the ones getting hired on large projects. When someone is hired in the film industry, they're hired for their specific taste, creative eye, and opinions. That contribution is literally their whole job. Outsourcing that task to AI is, within the industry, seen as an indication that someone is inexperienced or simply bad at their job. Crews don't want to work for those people, and audiences don't want to watch content created that way.
3. It's easy to "expect" that "one day" AI might become the way movies are captured if you don't actually understand the limitations of AI video generation versus the demands of filmmakers and the expectations of audiences. Putting aside the obvious stuff like continuity, shot duration, and resolution...GenAI is not color managed, it's not physically accurate, the results can't be copyrighted and it struggles with anything not in its training data (I.E., genuinely new ideas.)
This is NOT to say that this technology has no future in the film industry, obviously it does. But half the movies at the Oscars last year were shot on film, so the notion that all filmmaking is just going to turn into pixel soup being generated from prompts is just hilarious to everyone actually within the industry.