The thing about that is that they're relationship is left open to interpretation. They could have crushes on each other but they just as well could just be really close friends. When it comes to romantic relationships Nomura likes to leave them open ended so the fans can come to their own conclusions. Most likely Sora and Kairi's relationship as a couple will never be confirmed but it won't be denied either. Which goes for every relationship actually, especially Sora who "loves everyone" or at least has the capacity to love everyone.
Hmmm, I don't know where I sit with that. I guess that would be the best way to please everybody. But I'm not much of an "open to interpretation" guy. I need confirmation/closure.
But I guess that's just my problem to deal with then. Nomura can do whatever he wants. It's his story.