Tetsuya Nomura has dropped some information on Kingdom Hearts 3D (Dream Drop Distance), the upcoming series entry on the 3DS, in a recent Famitsu interview. The most interesting things he said related to Sora and Riku as the game's two playable characters.
Sora and Riku will have separate stories and will fight different bosses. They will also have different actions and control methods. While they will visit the same worlds, they will do so in a different order, and will rarely be in the same place at the same time. Unlike Kingdom Hearts: Birth By Sleep, however, the two stories won't be played in sequence. Instead, the game will switch characters suddenly and unexpectedly, perhaps leading to cliffhangers in each other's stories. Nomura says that this design decision was made in order to introduce a sense of surprise and tension into the story.
Sora and Riku may find themselves in new outfits at some point in the game, as well. Nomura hopes that seeing the characters in new clothes will help fans realize that Kingdom Hearts 3D is a new game in the series, not a remake. For now, however, they're wearing their usual duds in the game's screenshots.
Here is a permanent link to the Kingdom Hearts 3D trailer, as shown at the January Square Enix press conference: