Does this line in "The Blood of Olympus" imply something about "The Trials of Apollo"?

Question

In the last book of The Heroes of Olympus, The Blood of Olympus, just after Nico sends Bryce into the underworld and collapses, Nico has a dream wherein he sees Ella the harpy saying:

"Cheese is not good for harpies," she muttered. Then she scrunched up her face and chanted one of her memorized lines of prophecy: "The fall of the sun, the final verse." She fed Seymour more Cheetos.
"Cheese is good for leopard heads."
Seymour roared in agreement.
_{The Heroes of Olympus, book 5: The Blood of Olympus, chapter 31}

Does this line hint towards the next series, The Trials of Apollo, or at something else?

Answer 1

Yes.

We know that Ella has read the Sibylline Books - the books of prophecy that outlined the entire history of Rome, said to have burned when Rome fell.

"Never mind," Frank said. "Listen, we've got to protect Ella, take her with us."
"Of course," Hazel said. "The poor thing needs our help."
"No," Frank said. "I mean yes, but it's not just that. She recited a prophecy downstairs. I think... I think it was about this quest."
[...]
"The thing is," Frank said, "Ella remembers everything she reads. She said something about the page being burned, like she'd read a damaged book of prophecies."
Hazel's eyes widened. "Burned books of prophecy? You don't think - but that's impossible!"
"The books Octavian wanted, back at camp?" Percy guessed.
Hazel whistled under her breath. "The lost Sibylline books that outlined the entire destiny of Rome. If Ella actually read a copy somehow, and memorized it -"
_{The Heroes of Olympus, book 2: The Son of Neptune, chapter 36}

We also know that demigods have more powerful dreams than mortals - they can see things in places where they aren't while in a dream, communicate with other people... it's even revealed in The House of Hades that it's possible to die in a dream.

All this, plus the fact that Rachel Elizabeth Dare recited the Prophecy of Seven at the end of The Last Olympian (which means that it fits with previous example to have a prophecy about the next series at the end of one series), makes me assume that yes, this is a hint for The Trials of Apollo.

---

And of course, these lines make an appearance in The Hidden Oracle.

The voice spoke again: FIND ME.
This time it was so loud, it stabbed through my forehead like a railroad spike. I stumbled, falling to my knees.
"Hey!" Meg gripped my arm. "Get up!"
"You didn't hear that?"
"Hear what?"
THE FALL OF THE SUN, the voice boomed. THE FINAL VERSE.
I collapsed face-first into the stream.
_{The Trials of Apollo, book 1: The Hidden Oracle, chapter 9}

I'd say that this is fairly conclusive that yes, this is relevant in The Trials of Apollo.

Answer 2

Yes, this definitely relates to Trials of Apollo...Why? because Ella said - the fall of the sun - and Apollo is the personification of the sun...of course this could also mean Helios because he was a sun God and the fell part means that Helios had been forgotten and he fell to the bottom of the labyrinth - those who have read the burning maze book of trials of Apollo will know what i meant ... It could mean either Apollo or Helios but im going for Apollo, though one thing is sure - this refers to trials of Apollo and that is guaranteed