These are my Nightfall theory:

-Amy is slightly elf since Sophie somehow affected the womb(gosh that sounds weird)

-Lady Gizela is actually kinda helpful

-The door has forbidden secret

-Marella is a Pyrokinetic or Telepath

-Stina helps them

-A very short apology with the Songs that is broken up by something

-The caches are opened and take forever to decipher

-Kenric's has lots of secret news and stuff about Koralie.

-Fintan's starts with a warning and then a list of people he accidentally killed and people he murdered. There are slight details about Jolie.

-Lots of cute ship moments

-I think that either Sophie's mom is Oralie and her father is some random elf. Or her father is Kenric's and her mother is a random elf.

-Sophie transmits most of the info Amy needs secretly

-They have sister bonding time

-Oralie wants to resign but Sophie insists Kenric wouldn't want her to

-Sophie, Linh and Keefe have to go save a watery place

-Linh gets scared she can't control water with the Enhancing but her friends reassure her

-Sophie loses her gloves and is taken advantage of

-The rest of the group has to save them

-Sophie accidentally thinks about her secret and Fitz knows but doesn't tell her

-Baby Silfell is almost here

-The book ends on Lady Gizela betraying them (yet again), baby alicorn being born, or Black Swan vs Neverseen

-And someone important dies

-And lots more details.

These are just my theory's and probably won't even happen. I honestly think Shannon Messenger is going to just leave the Sophie ships open. But I hope on the last book she does an epilogue. Why can't Nightfall come sooner?