Arrow season 7's flashfowards have revealed a lot about the future of the show. Gone are the flashbacks to Oliver's life on the island; in season 7, there's a new storyline set in Star City 2038 that gives plenty of insight into what will eventually become of Oliver's son, William, and many of the other main characters on the show.
In the Arrow season 7 premiere, a series of flashforwards introduced actor Ben Lewis as an adult version of William Clayton; he reveals his identity to an aged Roy Harper by showing him an arrowhead that was given to him by Felicity in the present. Since, the new storyline has followed William and Roy to Star City, which is now in ruins. The flashforwards will remain throughout season 7, slowly teasing out just what's gone wrong in the future.
So far, three of the first four episodes of Arrow season 7 have included flashforwards, each dropping details about the future of Star City, the Queen family, and the various members of Team Arrow. William mentions to Roy, who for some reason is living in exile on Lian Yu, that he hasn't seen him since he left with Thea, which is likely a reference to Thea's departure from the series in season 6. This suggests that Roy may not return to Star City, which is a surprising development, considering that actor Colton Haynes is back as an Arrow series regular. This could mean that in season 7, Roy will only appear in the flashforwards and may not be the new Green Arrow after all.
As for the Queen family, it's been revealed that Oliver never taught William archery, and apparently both he and Felicity abandoned William at some point in his life. Felicity later formed a company called Smoak Technologies and, per reports William has heard, died (although it's not clear when this happened).
Arrow season 7's flashforwards have confirmed that two key members of Team Arrow, Rene and Dinah, are still alive in 2038. For a reason that has yet to be explained, Rene refuses to go anywhere near Star City, and Dinah has apparently trained Rene's daughter, Zoe, to be the new Black Canary. According to Dinah, Star City fell when the Glades rose up and built a wall to keep the authorities out. What none of this has provided much insight on is the identity of the new Green Arrow.
Since it's still early in the season, there's a lot left to be revealed about the whereabouts of other characters, such as Oliver, Diggle and his family, Curtis, and Black Siren. As Star City 2038's story continues to unfold over the course of Arrow season 7, more pieces of the puzzle are sure to fall into place.