Here's Absolutely Everything We Know About "The Princess Diaries 3"

Michael Moscovitz, Lily's brother, is Mia's main love interest from Meg Cabot's Princess Diaries novels. However, their relationship in the movies didn't go beyond the first one, and he didn't appear in Princess Diaries 2. If Mia and Nicholas aren't still together, it leaves the door open for a new king consort.

Lana and Principal Gupta weren't major characters and also didn't appear in PD2, but they were played by icons Mandy Moore and Sandra Oh, which is surely a good enough reason to put them in the script. Give Lana a redemption arc! Make Vice Principal Gupta the Genovian Minister of Education and have her iconically answer the phone some more!