They were and still are for the moment a great team. But this is expected. I don't think there has been an article about it, but Ai's mum said it in a Japanese newspaper.
Kim won't commit to playing all doubles tournaments next year, which Ai wants to do. Understandably Ai therefore wants a partner who she can play every week with. It's not that Kim isn't going to play doubles at all, just sparringly, like if she feels she wants to work on her net game or something and she feels physically fresh enough to do so she will play, but doesn't want to make an outright commitment to one player that she will always play.
Too bad! I'll remember that pair for a long time! They were great and could have dominated doubles tennis for a long time. But I understand Kim! It will be great maybe for them to play once in a while and win a title here and there