Some quick thoughts on how GPT/LLM/AI features could be added to browsers, phones, and operating systems, going from where we are today through to platforms-as-we-know-them-don't-exist:
A massive thing to think through is the ecosystem impact - abstracting away developer control has echos of the incentive issues that lead to no-one buying into the semantic web, but this time the the user agent is in control
So control over user agents will be an interesting battle - the big players will be bigger targets for publisher litigation; server-side agents will be much easier to block. It'll be game on to win consumer opinion quickly, and smaller players have an advantage here