I really hope that the CW Young Justice series happens. Manu Bennett's Deathstroke should be the main villain of the series. I also think they should try to adapt the Terra storyline from Teen Titans.
Since Brother Blood is a title that's passed on, a new Brother Blood (possibly more reminiscent of the comics) could be a major villain as well. H.I.V.E. has already been introduced on Arrow. H.I.V.E. members like Gizmo, Jinx, and Mammoth would be easy enough to pull off on a tv budget. There is already a pretty good foundation to build a Teen Titans/Young Justice show off of. Deathstroke, Brother Blood, H.I.V.E., and Roy Harper have all been introduced on Arrow already, and all are major elements of the TT/YJ mythos. Deathstroke already has mentioned his son Joe, who is better known as Jericho, a member of the Teen Titans.
Superboy and Miss Martian are said to be locks for this Young Justice show. Jericho and Roy Harper both already are confirmed to exist and could join the team. Hopefully Robin will be on the team, as it's not the same without him. But I wouldn't be surprised if Roy fills the Robin like role. If Robin isn't on the show, they will be disappointing a LOT of people though. He's at the center of every Teen Titans or Young Justice team.
There seems to be plans to have a tv Flash and a movie Flash, so the rumors about Cyborg and Robin being in Batman vs Superman don't necessarily mean they couldn't show up on Young Justice. I hope that both of them would be on the team. Maybe movie universe Grayson is already Nightwing, and Grayson on Young Justice could be Robin? CW has already tried to get a Dick Grayson series off the ground, so that could possibly be another element in favor of Robin being on Young Justice..
There was also a Raven series being developed at the CW at one point. It'd be great to have Raven on the team, maybe down the road they could even explore a Trigon storyline, with a slightly toned down Trigon.
If it were up to me... my team would be
Robin, Cyborg, Superboy, Miss Martian, Raven, and Roy for the first season.
Add Jericho in season 2, and Roy would leave the team and we'd follow his solo career for a while, and his relationship with Cheshire
The question is if the Justice League exist in this Young Justice universe. I guess since Superboy and Miss Martian are apparently involved with this series, then the JL would logically exist too... So does this mean that Young Justice would be set in a different universe than Arrow? Or maybe it's set a few years after Arrow?
The main thing suggesting that we could be getting a Young Justice/ Teen Titans show is the fact that all of these Teen Titans characters are being set up. It'd be so convenient for them to spin off a Teen Titans series at this point.