My first thought to reading what you wrote was fast denial, but the more I thought about it, I agree. We’ve seen vocal accents decline with globalized media, we’ve seen slang become more global, same with the entire English language. For years my text messages have been de-personalized by picking the autocomplete word choice where it makes sense, so why wouldn’t better LLMs expand that to even more written text?

That said, I suspect this won’t remain true in literary circles nor in certain professional contexts - where word choice is an art or signal, it will remain valuable. Politicians won’t sound like ChatGPT, for example. Think of some of the most famous modern politicians… they all have a unique way of speaking that makes it clear who’s talking.