SystemLink has found an interesting resume entry of a former Rockstar Leeds employee. In it he describes working on Chinatown Was and another unannounced title for the Nintendo DS. This unannounced title features a "full 3D open world" with a "complex hand to hand combat system". As he left the studio in 2010, it's unknown if the title is still in development or not. He mentions that he performed work on the PS3 version of L.A. Noire shortly before leaving so it may have been put on the back-burner so Leeds could focus on the PS3 and PC versions of L.A. Noire.  With the not so stellar sales of the DS version of Chinatown Wars and M rated games on the platform in general, it's hard to see why Rockstar would still be committed to the platform especially when they made a killing on the PlayStation Portable with the GTA Stories games. However, Sony did announce that Rockstar was developing games for the PlayStation Vita, the successor to the PlayStation Portable. Rockstar could very well be planning on either a cross platform launch of this unannounced title or have just simply transferred the game entirely to the PS Vita.

Source: SystemLink