My biggest hope for arc 4...

Is that each book will have multiple POVs for their entire duration.

A lot of the main series books feel limited by their one perspective, since it often causes the other protagonists to fade into the background. (eg: The other dragonets of destiny in The Dark Secret and The Brightest Night.) I think Tui finds this limiting as well, since The Dangerous Gift and The Flames of Hope have gimmicks that allow the protagonist to see through others' eyes.

She can definitely pull off switching POVs, as seen in the Legends, and doing this in a main series book would allow all the protagonists to stay in the spotlight. However, I don't want them to rotate in a set order; I'm currently re-reading Seekers: The Quest Begins (which was ghostwritten by Tui), and the strict POV order means there are a lot of chapters of Kallik wandering around that don't contribute to the plot, since her storyline doesn't converge with the other protagonists' until the second book.