Funny you mention autocomplete. The iPhone keyboard is a beautiful ML implementation. It runs on device and it is hardware accelerated. When things work users don't notice. Look at how people type of the iPhone. Sometimes they press a few keys away and it figures it out.
Putting a LM like GPT in the autocomplete has a lot of problems. You don't want your keyboard suggest too much. It is a Pandora's box. People will complain how the keyboard is putting words in their mouth.
I feel like it was far easier to type on the older iPhones, and there was a whole thread on HN of people with similar experiences. It's not just nostalgia; I still use an iPhone 5 sometimes, and its keyboard is superior. Idk how they regressed like that.
Putting a LM like GPT in the autocomplete has a lot of problems. You don't want your keyboard suggest too much. It is a Pandora's box. People will complain how the keyboard is putting words in their mouth.