Square Enix have dated the next Kingdom Hearts title to be released in Europe, Kingdom Hearts 3D: Dream Drop Distance for the Nintendo 3DS. It's coming out on July 20, and here's a short excerpt on the story and setting:
"King Mickey and Yen Sid prepare for an impending threat by putting Sora and Riku through the Mark of Mastery exam. Sora and Riku are sent into the Sleeping Worlds, where they will face enemies and allies that have never been seen before. If they can successfully complete the task they are given, they will be deemed true Keyblade Masters."