Gallery of all costumes here: http://shoryuken.com/2012/03/08/street-fighter-x-tekken-complete-costume-gallery/
Ibuki swapped with Yoshimitsu by the looks of it, he rocked a similar outfit in Tekken 5. For clarification check the description in the PS-Store there is a little story about all the costumes there. Her alternate isn't supposed to be anyone, just a different outfit for her.
Judging from the previous posts I'm going to guess the alternate costumes are going to come out around Halloween. This is just my guess. --- PSN ID: Doug_Drealer Tekken 6: Lars,Lili, Asuka, Xiaoyu SFxT: Asuka/Xiaoyu (Lars)/Lili