UPDATE: The new Green Arrow's identity has been revealed.
There's a new Green Arrow in town in the Arrow season 7 premiere, and the episode's shocking ending could hold the answer to the vigilante's identity. It's possible that Oliver's replacement is actually a time-travelling William.
At the end of Arrow season 6, Oliver (Stephen Amell) went to extreme measures to defeat Diaz (Kirk Acevedo) by turning himself into the FBI and giving up his secret identity. After Oliver was locked away in a supermax, Team Arrow broke apart and each member moved on with their lives. Since Oliver's incarceration, vigilante activity has all but vanished from Star City. The Arrow season 7 premiere changed that with the emergence of a new Green Arrow, who has arrived in the city with a list of targets. Oliver's replacement has stirred mixed feelings in Star City by inspiring Rene (Rick Gonzalez) to get back into action and firing up Dinah (Juliana Harkavy), who's now determined to arrest him.
Related: Who The New Green Arrow Definitely ISN'T
At the end of the episode, a man searching for Lian Yu encounters an aged Roy Harper (Colton Haynes) and reveals himself to be the adult version of Oliver's son, William, by showing him an arrowhead that had been given to him by Felicity (Emily Bett Rickards) in the episode's present-day storyline. Apparently, flash-forwards are the future of Arrow. Showrunner Beth Schwartz says Arrow will continue using them until the end of the series, replacing the flashbacks scenes that were a big part of the first five seasons.
Aside from the arrowhead, the flash-forwards in the premiere don't seem to have much to do with the episode's overarching plot. But what if the present and future storylines are somehow connected? Though many are speculating that the new Green Arrow is Roy Harper, another possibility is that the man behind the hood is William from the future. If adult William is trained by future Roy, he could conceivably have the skills of an expert archer, while also a more intimate relationship to the role. He could be traveling back to the past to save his father or someone else from a horrible tragedy, which would explain the purpose of his list.
The main problem with this theory is that time travel would be a major leap for Arrow, a show known for being dark and grounded, unlike the science-fiction heavy Legends of Tomorrow and The Flash, which deal with time travel on a regular basis. While a story about the main character encountering a future version of their offspring wouldn't be unusual at all for The Flash - especially since it's happening now in season 5 - it would be completely unexpected on Arrow.
Arrow season 4 did veer the show away from its typically grounded tone by introducing magic and other supernatural elements, but since season 5 Arrow has gotten back to basics, which makes it hard to believe that the series would change that now. That said, revealing William to be the new Green Arrow would certainly shake up the show in a remarkable way.