My comment was mostly about the current trend. In just 4 years we went from GPT-2 to GPT-4, and the pace seems accelerating. Only a fool points to the limits of current technology to make claims about future technology, the less foolish look at trend lines. The even less foolish have causal models, but even in this case, ChatGPT’s user trendline is faster growing than Reddit’s. Though this tells you little about whether they’re substitutes.