Iris. It really does depend on if there's some side quest in X/Y that could work for a female character to participate in. There really wasn't anything like that in B/W since Musicals were just a non-interactive version of the video game Contest appeal round. At least there was room for the writers to add in battle rounds in Contests when they were first introduced. Plus, I think that they wanted Ash to travel with two characters who are Gym Leaders in the video games like he did in the original series as an homage of shorts. If X/Y either bring back Contests or introduce some new sidequest, I don't see why they wouldn't have another female co-star.