This may seem like small peanuts compared to AI ending the world, but I think it will be technically possible to de-anonymize most text on the internet within the next 5 years.
Analysis of writing style and a single author’s idiosyncracies has a long history of being used to reveal the true identity of anonymous authors. It’s how the Unabomber was caught and also how JK Rowling was revealed as the author of The Cuckoo’s Calling.
Up until now it was never really viable to perform this kind of analysis at scale. Matching up the authors of various works also required a single person to have read many of the author’s previous text.
I think LLMs are going to make textual fingerprinting at a global scale possible within the next 5 years (if not already). This in turn implies that any archived writing you’ve done under a pseudonym will be attributable to you.