If the 2020 reprint is successful enough to continue through the rest of the series, they will change the ending.
The Jewel Princesses and the Missing Crown ends with the four princesses defeating Lord Bleak and Princess Rudgrin and kicking them out of the Jewel Kingdom again... but times have changed. Popular children's media of The New '10s, immediately preceding the reprint, has heavily focused on redemption arcs and less on Black-and-White Morality. It was never really Rudgrin's fault that she was on the wrong side; she was exiled as a baby (or perhaps born in exile) and only ever knew her father's side of the story. Given the reprint's changes largely involve removing the Dark Is Evil elements, the authors might have noticed that themselves, so she might well be on her way to being forgiven for her crimes, even if Lord Bleak isn't.On top of that, the reprint also changed the way Lord Bleak's people look, describing Dreadlings (including Rudgrin) as having eyes that look like "shiny black stones." You know, gems. With that plus Rudgrin's role as the princess of Castle Dread, it's looking at least possible, if not likely, that the ending will change to allow Rudgrin to be redeemed and welcomed as the fifth Jewel Princess (though they'll probably change her into a normal girl; Black Eyes of Evil aren't very marketable). The Opal Princess? Hematite Princess? There are black gems to spare out there.
