Hi all, I've been lurking for over a year now, and thought I'd finally join in and post predictions before we get a reveal of the new sets!
$19.99, 121 pieces-Either Draco's Buckbeak's encounter, or Siruis's escape with Buckbeak. Something with a large mold to justify the low piece count.
$49.99, 345 pieces- Gryffindor common room, based on the scene in PoA with the Fat Lady's portrait. Includes Percy (in the movies, him pushing through he crowd shouting about how he's head boy is one of his last scenes with lines), some sort of play feature for the portrait to move, maybe Filch, since he hasn't been included in a while.
$79.99, 654 pieces- Durmstrang Ship
$99.99, 990 pieces- Probably some kind of display piece again, since they like to give us those. A buildable Firebolt maybe? A microscale maze from the 3rd task, similair size to the chess board from last year? Buildable marauders map? Etc.
Advent Calendar-If they're sticking with PoA/GoF, hopefully it will be Hogsmeade- themed, but I feel like it's more likely to just be themed around the 2nd movie, similair to how last year was based on the first movie.
$469.99 (D2C)- I'm on board the Gringotts/Leaky Cauldron/ Borgin and Burkes train, and I'm ready to be disappointed.
$49.99,671 pieces- Niffler, probably the only Fantastic Beasts set
$89.99, 777 pieces-Shrieking shack, with werewolf Lupin, the trio in their hospital wing outfits, Sirius and Peter
$119.99- A long shot, but I think the 2nd task has to be included here somewhere, and I like @BrickFunatic's idea putting it with another piece of the castle. We haven't gotten a library yet, and that's the part of the castle we're in right before the task, so I'm hoping it will be that. Also includes a viewing platform (with a feature to launch Harry off of it), a small underwater bit with a mermaid, all the champions, Neville and some gillyweed, and some (but probably not all) of either Ron, Hermione, Cho, and Gabrielle to be rescued.