1. The "Heroes of Olympus" Series: While this series is technically separate from the *Percy Jackson & the Olympians* books, it features the same characters and is considered part of the same universe. It's highly likely that Riordan will continue to write stories set in this world, possibly featuring new characters or revisiting the old ones.
2. Spin-offs and side stories: Riordan has already written several books that expand on the world of *Percy Jackson*, including the *Magnus Chase* and *Trials of Apollo* series. He could continue this trend, perhaps focusing on different demigods or aspects of Greek mythology.
3. A *Percy Jackson* reboot: The Disney+ series is currently in production, and it's possible that the success of the series could lead to Riordan writing new books to expand upon the show's story.
4. Re-telling or re-imagining of the original series: Riordan has mentioned that he could potentially re-tell the *Percy Jackson & the Olympians* stories from a different perspective or with a new focus.
5. Never say never: Even if there are no immediate plans for more *Percy Jackson* books, it's always possible that Riordan will revisit the series in the future.
Ultimately, the best way to stay up-to-date on the latest news is to follow Rick Riordan's social media accounts and check his website for announcements.