The iOS port of The World Ends with You, The World Ends with You: Solo Remix contains a secret ending that could hint at the possibility of a sequel. Here is an image of that ending:
New 7 days, huh? Could this be a tease for a sequel to The World Ends with You, or maybe some other related project? The game’s director, Tatsuya Kando, recently stated in Famitsu magazine that they are indeed working on other projects. Hopefully we’ll find out more at Square Enix’s conference this weekend.
Source (http://www NULL.siliconera NULL.com/2012/08/31/new-7-days-says-a-teaser-in-the-world-ends-with-you-solo-remix/)