If you have a savedata of "Street Fighter X Tekken" in your console, it will automatically unlocks five extra costumes for them. Beware! These costumes aren't the ones of the USFIV preorder, there are the ones from SFxTK. As Decapre isn't in the game, they give her the Cammy's one.

Costume	How to unlock
"Bad girl" Decapre costume (SFxTK Cammy)	Get a savegame from Street Fighter x Tekken.
"Military" Poison costume	Get a savegame from Street Fighter x Tekken.
Hugo viking costume	Get a savegame from Street Fighter x Tekken.
Rolento plumber costume	Get a savegame from Street Fighter x Tekken.
School uniform for Elena	Get a savegame from Street Fighter x Tekken.