Their eShop listing for the soundtrack mentioned that it would be heading to iOS later this year. Although the listing is still there, the text mentioning an iOS release has been removed.
The soundtrack goes by the name of Subarashiki Kono Sekai Crossover (where Subarashiki Kono Sekai translates into I’s A Wonderful World, the Japanese title to TWEWY) The new soundtrack will feature new iOS versions of songs, Kingdom Hearts 3D arrangements and new tracks just for this soundtrack CD.
S-E’s countdown clock for TWEWY is set to end this weekend, so we’ll find out what’s happening soon enough.
Update [August 26, 2012]: The countdown clock on Square-Enix’s site is for a direct iOS port of The World Ends With You. TWEWY Solo Remix available for iOS in Japan and elsewhere for $18 on the iPhone and $20 on the iPad with revamped sprites and backgrounds. The game is available for iPad 2 and iPhone 4 or higher. Unfortunately TWEWY Solo Remix is not available for iPod Touch owners, which is excluding a large fanbase/userbase and is a poor move from Square-Enix. The World Ends With You: Solo Remix is worth the pricetag if you’re a fan of the game or haven’t played it yet.