
Yeah that's what I read in an interview of the director of the game, Tetsuya Kando in a The World Ends With You post-release interview by IGN (published on January 22nd, 2009), they talk to him who first states that the game was not initially created with a sequel in mind when asked about the possibility of The World Ends With You 2.
IGN: How has the situation with this license changed since the game’s initial pitch? Was it originally designed as a one-time game, or was there always a possibility for sequels? Now that the game has sold surprisingly well, may we see another game in the series?
Kando: The game’s concept has not seen any drastic changes since its inception, but it was the first time our team decided to develop for the Nintendo DS hardware, so figuring out how to bring out the best in this hardware was a constant process of trial and error. Our objective was first to create a complete product, so we never really had a sequel in mind during development.

However when asked again later on about the possibility of The World Ends With You 2, Kando seems much more open to it and in fact, sounds as if a sequel will definitely happen.
IGN: Many fans of the game have now put in plenty of time with the game, and we’ve of course said our piece on it with our awards. Is it time to start thinking about a sequel? Can fans expect one, or is that something that’s still being worked out internally?
Kando: We’re very thankful that this title has been received so well, and as we see that there is demand from both Japanese and American fans, we would definitely like to consider the possibility of a sequel. Since it is not possible to get right into development at this moment, please give us a little more time.
At the end, he once again states that he would love to do a sequel if presented the opportunity.
IGN: Obviously you can’t share everything with us, but what could the future hold for The World Ends With You? Obviously we’d love a sequel, but the soundtrack, pre-release comic . . . there’s a lot to work with here. Perhaps an anime or manga series?
Kando: Personally, I think we’ve created a game that has a lot of potential to expand, so if given the opportunity it would be wonderful to take on the challenge. It would be such a waste if this was the end for The World Ends With You!

So that's all he said, and most likely we can wait for another sequel. That's just what he said, or what IGN made a fake interview, but what can I say let's just wait and see.
That's all for now