Here's why:
* Nico's popularity: Nico has a huge fanbase and is a beloved character in the *Percy Jackson* universe. Riordan has acknowledged this and hinted at potential future stories.
* The Trials of Apollo series: Nico plays a significant role in this series, appearing in multiple books. This suggests that Riordan might continue exploring his character development.
* Spin-off series: Riordan has previously written spin-off series featuring characters from his main books (e.g., *Heroes of Olympus*). A Nico di Angelo series could be a future possibility.
* The potential for an older Nico: The *Trials of Apollo* series ends with Nico still a teenager, so there is room to explore his journey as a young adult in future works.
Ultimately, only Rick Riordan knows his plans for future books. However, given the popularity of Nico di Angelo, it's definitely a possibility that we might see more of him in the future.
Keep an eye on Rick Riordan's official website and social media for any announcements about new projects!