I agree, GPT-4 is still the undisputed king in LLMs, it's been a wee bit more than a year since it came out. I'm sure that the quality of GPT-5 will depend more on a carefully curated training set than just an increase in their dataset size, and I think they're really good at that.
Also, very few people know as much as sama about making startups grow, so ...
PS. I'm not even a fan of "Open"AI, but it is what it is.