Princess Diaries is currently in development.

THR reports that a third Princess Diaries film is currently in the works. The Disney film will be written by Reacher and ‘Quantum Leap scribe Aadrita Mukerji. Anne Hathaway is not on board yet but has expressed interest in returning to the franchise. The 2001 film also starred Julie Andrews, Héctor Elizondo, Heather Matarazzo, Mandy Moore, Caroline Goodall, and Robert Schwartzman. A sequel was released in 2004 called Princess Diaries 2: Royal Engagement. Garry Marshall directed both films.
Synopsis of the 2001 film.
Shy San Francisco teenager Mia Thermopolis (Anne Hathaway) is thrown for a loop when she learns the astonishing news that she’s a real-life princess! As the heir apparent to the crown of the tiny European principality of Genovia, Mia begins a comical journey toward the throne when her strict and formidable grandmother, Queen Clarisse Renaldi (Julie Andrews), shows up to give her “princess lessons.”