On January 1st, a banner describing "New card box, Valkyrie's Rage, has been added" had appeared In Japanese App Store. It seems that was an accident since the banner was replaced with another one mentioning "Neo-Impact", the card box that had been released recently.
A banner with "Valkyrie's Rage"
A banner with "Neo-Impact"
This image looks fake, but some people says they saw this pack in the game.
So here is a list of expected cards. Those cards are picked based on the name of the upcoming booster pack and decks that standard duelists use in the game.
It is expected that the booster mainly contains Fairy-type monsters and their supports. Check currently buildable Fariy decks and useful Fairy cards.