I think the killer app will involve adding more layers of AI to make something that is closer to an agent than a simple prompt completion engine. Maybe a more self-contained system that has an internal cycle of asessment, generating prompts, executing output, and readjusting prompts. These agents could conceivably work on long term, complex projects with minimal supervision or interaction. If a general purpose system can get a foothold and be even 10% as good as a person, it could be enough to fundamentally reshape the workforce.