It's no surprise that the CW wants a third superhero show. Their other 2 other succesful, and even if they're bad, not many people actually stop watching. CW has been spinning something for a while, recently bringing in a third superpower, Atom, into the third season of Arrow. It's been confirmed that We will see Ray Palmer suit up eventually, but we don't know if that'll be in [Arrow](series:720988), or the more likely and science fiction-y [The Flash](series:1068303). Here is the top contender for a new show:
This is the one I have most faith in for many reasons. See, what CW does is make a platform for the less popular DC characters in order to make it a better known character when they're on the big screen. Flash is, arguably, a "big" hero, but he's not in the top 3 when you ask about characters from the Justice League. Same with Green Arrow. Cyborg will be well established by the time his solo movie is here in 2020, just like with Flash by 2018, and Green Arrow if/when he gets a movie.
Characters We Want But Can't Have
There are a lot more characters we want but can't have for many reasons. So let's take a look at those that are just beyond our grasp:
Hal Jordan, to be specific. Green Lantern and Green Arrow are known for the best crossover storylines in comics. Green people thing I guess. But we won't see it for so many reasons. FX is one. CW sucks quite a bit at special effects. Especially with explosions, but still. Green Lantern is too big a superhero, and his name is still marred after Ryan Reynolds' crap fest. But the closest we'll get to that is the Ferris Air easter eggs.
The founding member of Teen Titans, Nightwing is an obvious candidate. It can open doors to so many people, who can open doors to more people, eventually making a full TV Justice League. That's a problem as well as a gift. A problem, again, because of the FX. But anyways, TNT already has the Teen Titans rights, and it would be hard to have Nightwing on CW without referencing Batman, and once Batman is in the picture, Green Arrow is just a cheap copy cat. 2/3 of his main villains are Batman's too (Deathstroke and Ra's Al Ghul).
Hourman, which CW already said they're developing, can be seen as a risky move for the CW. He's a lesser known hero and founder member of the Justice Society of America. Not the League. Society. The old version. It would be pretty hard to bridge the gap between the onscreen Justice League and unmentioned in every way Society. I don't know much about him, so I'll stop there.