Although Kingdom Hearts 3D has been out in Japan for a month now, today marks the release of the KH3D Ultimania, which contains a great deal of information on the game including staff interviews.
Some choice quotes have been pulled from director Tetsuya Nomura concerning the future of the Kingdom Hearts series while clearing up some of the mysteries behind KH3D.
Regarding KH3D, there are currently no plans to create a Final Mix version of the game, Asked if the game's secret ending had anything to do with a possible Kingdom Hearts 3, Nomura simply said, "Use your imagination, you'll eventually find the answer."
Nomura says that they've already begun to move forward with new entry(ies) in the series. In fact, he believes that they can make an announcement on the next KH game "before long." As to whether or not that game could be Birth by Sleep vol. 2, Nomura said, "I used 'A Fragmentary Passage' without regard to its context. What I mean is, there's a story for Volume Two, without using that scene. I can't say there isn't a possibility of making it, but there are no plans for it right now."
In addition, the series producer would like to see Pixar works make it into the games someday.
Multiple titles are also in the works at Square's Osaka studio (the developers behind BBS and KH3D). Hopefully we'll see what they've been up to sooner rather than later.