Square Enix just loves to drop hints to things that are definitely in progress. Tetsuya Nomura, co-creator of The World Ends with You, did just that about TWEWY in an interview with Nintendo Dream (translated by Andriasang).
The interview was in regards to Kingdom Hearts: Dream Drop Distance, but Nomura's hint about TWEWY pretty much stole the show. He explained that Square Enix decided to add voice acting to Raimu for her appearance in KH3DS "out of consideration for the future of The World Ends With You series."
When asked about TWEWY's future, Nomura half-heartedly sidestepped the question with: "Regarding The World Ends with You, I can't say anything at present, but there probably is something."
Translation: there is something.
Square Enix likes making sequels of games whether they need them or not, and it seems like TWEWY is next up. I loved TWEWY, but I have no idea how a sequel for the game would even work. If the story is as discombobulated as Final Fantasy XIII-2's story in order to make something plausible, count me out.