According to a recent Nintendo Power interview with Takashi Tezuka, New Super Mario Bros. for the DS will feature the return of the beloved koopalings. This welcome addition should significantly boost the game's boss element. Tezuka also confirmed that Bowser and Toad would make appearances. As for the green dinosaur, since the game is a throwback to the NES Super Mario Bros., "Yoshi doesn't really fit," says Tezuka.
Tezuka also noted that the game will be set in the Mushroom Kingdom and that there will be no boss battles in 2-player mode, no WiFi connectivity, and no microphone functionality. Finally, when questioned about the possibility of a console-bound Mario side scroller, Tezuka replied, "The probability is not zero, but no further comment at this point." Then he just laughed.