Konami announced they are developing Contra 4 (working title) for the Nintendo DS. Contra 4 takes place after the events of Contra III: The Alien Wars and introduces a new alien force, the Black Viper. Contra 4 sticks to the series 2D side scrolling shooter roots and it introduces a dual screen battlefield. The other new element Konami revealed is a grappling hook that lets players grab on to the environment and quickly switch positions. Like the other Contra games, Contra 4 will have two player co=op play, but Konami has not announced if it will only be local multiplayer or if they will utilize Nintendo WiFi.
Something else to note is Contra 4 is not being developed in house. WayForward Technologies who made Barbie 12 Dancing Princesses and Sigma Star Saga is doing the development work to get Contra 4 on store shelves later this year.