Executive Producer Andrew Kreisberg says Nightwing is his "fantasy" character to add to the show, but apparently that's unlikely to happen any time soon. According to Digital Spy, he and Marc Guggenheim chatted with the press at this year's Comic-Con and said WB's latest movie announcement (untitled Batman/Superman project) makes things far more complicated.
"We've heard the fans and we're very well aware that they would like to see Nightwing and various other Bat-characters on the show."
"[But] that is a little bit out of our control, [and] I think [that movie] announcement made it a lot more out of our control!"
They said they'd still love to use him, but I wouldn't expect the first Robin to show up in the upcoming season, Viners. Besides, we're getting plenty of other characters to look forward to -- Black Canary, Bronze Tiger, Deadshot, Brother Blood, etc. In case you haven't seen it yet, here's the trailer they released at Comic-Con. Don't watch it if you haven't finished season one!
Arrow will return October 9th.
Source: Digital Spy