Yeah, Nightwing is Robin. You see, in the comics, Dick Grayson, the first Robin, after joining the Teen Titans and facing The Judas Contract, in an attempt to distance himself from Batman, dawned his own new identity; Nightwing. Since the series jumped ahead 5 years, similar to when the comics skipped one year after Infinite Crisis, a grown-up Robin emerges as Nightwing (following the flow of the comics). Hope that helps
Dick Grayson is Robin in YJ:I. There is this whole complicated thing about how Dick becomes Nightwing and is replaced by Jason Todd, who dies (in the sacred hall of dead heroes thing in episode 9) and is then replaced again by Tim Drake, the Robin in the new show. There are actually 5-6 Robins in total (not sure). I don't know if they will have all of them though... that's all I know. :)
