I mean, it's possible to load LLMs onto a smartphone today. The utility is limited though, and if iPhone 19 still has arbitrary application memory requirements then I think it's safe to say they won't be using the most complete models. At the end of the day, OpenAI's "huge-ass LLM as a service" will probably be relevant longer than you think it will be. Local inferencing might be able to do simpler stuff (eg. compose assistant speech) but this is already possible with pruned models and CPU acceleration.
The bull mindset is fun to watch unfold (especially here on HN) but I think people should temper their expectations.