As of Arrow's latest episode (season 7 episode 6, "Due Process"), it is now apparent that no one on Team Arrow has taken up Oliver Queen's mantle as the new Green Arrow. While the greater portion of the team had been eliminated as suspects in earlier episodes, a battle utilizing most of the core cast confirmed there was no way that most of few remaining suspects could be the new Emerald Archer, whose true identity has confounded the police, the anti-terrorist group ARGUS and Star City's criminal element.
The question of the new Green Arrow's identity has been one of the series' major mysteries since the start of season 7. The new Green Arrow first appeared in the season 7 premiere, targeting a group of gun-runners. Their actions got the attention of what remained of Team Arrow, all of whom had officially retired from vigilantism in the wake of Oliver Queen's arrest in Arrow's season 6 finale. Unofficially, however, there was a chance that some of them might have continued to fight crime on-the-down-low, though most of them had elected to find ways to protect Star City in a legally authorized capacity.
The episode confirmed that Rene "Wild Dog" Ramirez was not the new Green Arrow, by simple virtue of the fact that he was the first one to see the new hero in action. It was also shown that Dinah Drake (once Black Canary, now a Captain in the Star City Police Department) wasn't Oliver Queen's replacement as she was part of the team of cops who were working to catch the new vigilante. It was also assumed it couldn't be Felicity Smoak, given her lack of combat skills and her living in another city at the time the new Green Arrow first emerged.
Following the first episode of season 7, the prime suspect was John "Spartan" Diggle. Not only was he Oliver Queen's hand-picked successor but he had taken up the Green Arrow mantle on two earlier occasions and had access to a Green Arrow costume, which Oliver Queen had given Diggle before being imprisoned. Though Diggle directly denied being connected to the new Green Arrow in season 7 episodes 2 and 3, "The Longbow Hunters" and "Crossing Lines", there was still a chance that he was lying to protect the rest of his fellow vigilantes should he be caught in the act.
Diggle was officially eliminated as a suspect following episode 4, "Level Two". It was here that Rene Ramirez and Dinah Drake both got a good look at the new Green Arrow and showed no signs of recognizing them under their hood. Viewers also got to see the new hero and discovered that whoever they are has far lighter skin than John Diggle.
Arrow season 7 episode 6, "Due Process", saw almost all of Team Arrow united in a mission to stop crime-boss Ricardo "The Dragon" Diaz from burning Star City through a massive gas line explosion. Curtis "Mister Terrific" Holt, Rene Ramirez, Felicity Smoak, Dinah Drake and John Diggle were all present and accounted for during the fight, along with the new Green Arrow, who fought alongside John Diggle himself to bring down Diaz. At the same time as the battle, the villain Black Siren (currently masquerading as both a lawyer and the Laurel Lance of Earth 1) was visiting Oliver Queen in prison, shutting down the theories that suggested Black Siren was seeking redemption as the new Green Arrow or that Oliver Queen was somehow sneaking out of his prison cell at night to become the Green Arrow once more.
This means that, whoever, this new Green Arrow is, there is no chance that they are numbered among the ranks of last year's core cast. However, none of this eliminates Roy Harper, whom it was suggested might return to Star City to take up his former mentor's identity. It also does not disqualify the idea that William Clayton, Oliver Queen's son, might travel back in time to become the hero his father's city needed. Whoever the new Green Arrow is, the mystery is sure to add tension to the storyline of Arrow for a little while longer.