Speedy becoming evil? Eh... In the YJ universe, the most evil he'll get would probably be if they show his Heroin addiction, but the chances of that is really,really low. Or if they introduce the Outsiders.
In the comic verse, he does team with Jason Tood/Red Hood/Second Robin and Starfire. They became known as Red Hood and the Outlaws.
He was addicted to Heroin in the cross-over comic series of Green Lantern and Green Arrow. I heard it was just to add more "character" to him, the same reason was used to when they killed off his daughter Lian. That just what I heard.