ToyWiz has been shipping out their masquerade ponies earlier than planned. As such, we can see the backcard for Sunset Shimmer which includes a small blurb about her. It reads:
SUNSET SHUMMER knows a magical path to faraway adventures! Years ago, she was also a student of PRINCESS CELESTIA.Rumor has it that Sunset Shimmer will make an appearance in the show. This may hint as to what she's all about. We'll see!
(via Equestria Daily)