UPDATE: The new Green Arrow's identity has been revealed.
The season 7 premiere of Arrow reveals that a new vigilante has emerged to take Oliver Queen's place as the Green Arrow. The mysterious hooded archer's identity remains a secret, but there's a good chance that the man behind the hood is the original Green Arrow's former sidekick, Roy Harper (Colton Haynes).
Thea Queen's boyfriend, Roy Harper, was trained by Oliver (Stephen Amell) during season 2. He was eventually added to the team, dressed in red, and given the code name "Arsenal." Roy remained with Team Arrow until season 3 when he fooled everyone into believing that he was the Green Arrow to ensure Oliver's secret identity remained intact. In season 6, Diaz (Kirk Acevedo) captured and tortured Roy in an effort to force him to testify against Oliver. Soon after he was rescued, Roy and Thea left Star City together on a mission to destroy the Lazarus Pits. This moment marked Thea's departure from the series.
Related: 9 Big Questions We Have After Arrow's Season 7 Premiere
In Monday's episode, a new Green Arrow rescued Rene (Rick Gonzalez) from gangsters and avoided capture by Star City police. The vigilante seems to have a list of people to eliminate, much like the one Oliver used when he returned from Lian Yu. He also uses Oliver's trademark line, "You have failed this city". Whoever this Green Arrow is, he's clearly inspired by Oliver's season 1 persona, "The Hood".
At the end of the episode, a flash-forward scene shows a grown-up William Clayton meeting an aged Roy Harper. Roy, who will be back as a series regular for season 7, may be a key character in both the present and future storylines.
It's possible that Roy is back in Star City as the Green Arrow. Oliver's arrest finally gives Roy a reason to return to Star City for good. Now that Oliver's identity has been exposed, Roy is in the clear. Roy taking up Oliver's mantle would make sense, considering how much being a hero meant to him. With Oliver behind bars, it's conceivable that Roy would want to continue Oliver's mission of protecting Star City.
The only problem is the new Green Arrow's list of enemies. Something must have happened to Roy's life to explain why he would hunt down and kill specific criminals. If Roy is indeed the new Green Arrow, he could provide a sense of hope that Star City has lacked in the five months since Oliver's incarceration. He's also a person who the former members of Team Arrow could trust and rally behind until Oliver escapes from prison.