In a recent article of Famitsu, a New Years card from Gust was sent out to them and Gust might be hinting a new Atelier game through the new character model that was drawn in the card. The girl who is holding a giant key might be the next character that will appear on the new Atelier game.
As of now, we will consider this a rumor until Gust formally announced this. It sure is exciting to see another Atelier game coming but could this be on the PlayStation platform? Or XBOX 360? My guess would be PlayStation 3!