“I’m really happy that the game was so well received in North America. I definitely want to make a sequel. I’m very busy working on other titles right now, but when the time is right, I would love to make another installment of The World Ends with You.” – Tetsuya Nomura

I’m not too sure how well The World Ends with You sold, but there’s no question that it had an overwhelmingly positive critical reception. There are also a ton of DS owners that greatly enjoyed the title. It’s nice to know that there’s a good chance we’ll see a sequel in the future… Perhaps on the 3DS?

http://www.nintendoeverything.com/46567/

Eh, I've never played the first one, but I've heard it's really good.

I thought the lead designer for the game said they wouldn't make another because the 'SquareEnix Execs' said no.  Something about 'We're no longer encouraged to make original ideas'.