A quote I heard recently that really resonated with me: "Soon, asking a writer if they use AI will be like asking a photographer if they use Photoshop" – e.g., it's a foregone conclusion, and the best artists will generally adapt to using the best tools available
I don't think "AI" is the way most people would complete that sentence. Perhaps "Word"? Or "LibreOffice" if "Photoshop" were replaced with "Gimp"? Personally I use Emacs or Vim. You could incorporate AI into any of those tools, but how exactly? And would it be a core part of the functionality? And would it be something that the best artists make much use of?
If you used AI to make the spelling/grammar checker more reliable, probably most people would use that (assuming no privacy problems), but if there's an AI-driven autocomplete for sentences probably a lot of people, including the best artists, would turn it off, just like I turn off the autocorrect on a word processor today.
If an AI can complete the sentence, then perhaps the sentence isn't worth completing, at least if we assume that the reader is as clever as the writer and has similarly sophisticated tools. Perhaps the AI-driven tool should instead put some kind of wavy line under the second half of the sentence to indicate that it's boring and obvious and doesn't need to be there.