The World Ends with You is for an iOS port of the DS game, a leak on the Square Enix's Japanese eShop has apparently revealed. A listing for an upcoming soundtrack of the game disclosed that an iOS version would be released later this year. It also mentioned that the port will feature new music, including arranged tracks from Kingdom Hearts 3D.
Square Enix quickly deleted the incriminating info, but Siliconera has the screencaps for evermore. Hopes of that elusive sequel appear dashed once more, but we hope we're proven wrong.