I wonder if it will extend to generating off-screen content like interviews and paparazzi photos.

I think you're right though, it will happen. Probably in some cheap corner where it makes economic sense, then to the bigger roles. Perhaps you don't want to manage thousands of extras for battle scenes, paying them and feeding them. Just generate them. Then eventually you also end up doing away with minor speaking roles, then the big ones.

The plot can also be generated. If you like fantasy, the AI can generate a new world for you with its own lore.