Kingdom Hearts producer (and theoretical Final Fantasy Versus XIII lead) Tetsuya Nomura told Famitsu that the appearance of The World Ends With You's Neku Sakuraba in Kingdom Hearts 3D: Dream Drop Distance portended other things for the character in the future.
According to Andriasang, Famitsu asked Nomura if Neku's appearance provided notice of a sequel to the Shibuya-based DS RPG. Nomura didn't quite confirm a sequel, but he did say that the appearance suggested "something" that Square Enix is working on.
Last year, Nomura said he wanted to make a sequel to TWEWY "when the time is right." Perhaps the time will be even closer to right two minutes from now, when you've watched the new trailer above (featuring Neku).