I'm not sure I follow. The UI for ChatGPT is still on your browser, yes? So it is still HTML and CSS. The fact that it is generated content instead of static doesn't change the front-end tech that renders it on-screen.
If you are saying the UX paradigm will no longer be "pages", that I can believe. But the browser still is the most common way to access content, regardless of what generates that content.
Maybe then "interactivity" becomes more important and sort of a distinctive feature?
More move from "web of documents" nature of Original Internet to the "web of applications" idea?
Aren't all examples of where Chat is better just more simple Q&A type apps?
I've worked in EMR software for 10 years and I will tell you this - no doctor wants to ask the EMR for information, they want it to be smart enough to show exactly what they need at exactly the right time. For example, if I am viewing a patient on specialty medication X I want relevant labs, medical history, current med profile and any allergies. A doctor would be furious if they had to spend their time going "what allergies does this patient have?"
Not that EMRs are the pinnacle of good design, but this is the reason why there is so much information per page.
In my experience - if the user is searching for information, then typically your UI is not intuitive and or not making good use of the screen real estate.