I mean, I damn well hope so. From what i've seen in vids, and what i've heard in story, Xion will be very improtant and do something, but for all we know, it's just like the movies, the only parts someone does something in are in the commercials. Now I doubt Xion will be useless and annoying, but she's a part of Kairi(supposedly), and what if Nomura strongly bases her character on Kairi's, and she's just a plot tool like kairi was. Oh man, I hope not. I cannot stress how much I really think it won't be the case, but lets think of this as a "what if..."