Any self-learning system can change its own weights. That's the entire point. And a text-processing system like ChatGPT may well have access to state-of-the-art research. The combination of those two things does not imply that it can improve itself to become secretly AGI. Not even if the text-completion algorithm was even more advanced. For one thing, it still lacks independent thought. It's only responding to inputs. It doesn't reason about its own reasoning. It's questionable whether it's reasoning at all.
I personally think a far more fundamental change is necessary to reach AGI.