> it’s likely a matter of months before authentic-looking video of newly invented Seinfeld bits like this can be generated by anyone with a few basic, not-especially-technical skills

Let's define "authentic-looking video" as a clip at least 30 seconds long, with good lip-sync, integrating realistic voice, without significant logical incoherence and able to follow prompts that impact both the "scenario" and the "decor" of the video at least reasonably well. That won't happen in a year and there is a good chance it won't happen in 2 years. Production-ready quality for minute-long videos involving an actual plot, even after human post-processing (excluding very significant human involvement) will not be there in the next 5 years.