Porn could definitely be a killer app for LLMs, and I strongly hope that open source models win out for a number of reasons, but I'm not sure it will happen. Microsoft and OpenAI have quickly gone to great lengths to try and limit the amount of output they find offensive, and those efforts have been fairly well received by the general public.

Despite the size of the regular online porn industry, it still gets strangled by payment processors. There is plenty of appetite out there for restricting porn in various ways.