The February 18, 2010 issue of Famitsu Weekly magazine has included an article on the Kingdom Hearts series. This article discusses Sora's involvement in the series, and contains an interview with the series' director, Tetsuya Nomura. This article confirms that Kingdom Hearts III will eventually be released. HEARTSTATION.ORG have scanned this article and translated the interview, both of which can be seen below.
At first his design was like that of an anthropomorphic lion, with ears and a tail too. His weapon wasn’t the Keyblade either; it was something like a chainsaw. He had the tail so he was more along the same design line as the Disney characters. The Kingdom Hearts project was happening during the production of Final Fantasy VIII, and since the series was already progressing and Zidane from Final Fantasy IX had a tail, Sora’s animal traits were removed.
Finally, during an exchange of ideas with the Disney staff side, the parts that were too straight line were modified into curvier shapes (The weightlessness of his pants and shoes were striking features.) So in one night, the Sora we know now was completed.
In the secret movie in Birth by Sleep, Sora’s long awaited re-entry implies that future developments are in the works. Therefore, please look forward to the appearance of Sora’s future activities when they are prepared. Though saying that, I can’t say what kind of title it might become. Concerning Kingdom Hearts III, since there is demand from the current fans around the world, I will do my best to bring it into realization as quickly as possible.