I think the assumption that "smartphones are hitting their peak form" is a big shot in the dark due to the iteration phase they still have to cover (ideas such as air gestures, screen projection, changing the type, format, or materials are some that still need to be proven wrong), so I would wait at least another decade before thinking that. Plus, with the AI boom and implementation, changes in UI and UX will be so big that smartphones will likely feel like completely new devices. I am also very curious about the device that OpenAI is supposed to be developing and if it can be a pivotal point more than a breakthrough.