Last chance. If you're not caught up on Arrow and/or The Flash don't read.
Recently a trailer for the remaining season of The Flash has been posted, and one of the things shown is Oliver Queen in a different wardrobe. It's safe to assume that The Flash is heading in the direction of DC's Flashpoint Paradox. This storyline could heavily influence Arrow in a Spider-man: Brand New Day kind of way. The few seconds we see of Oliver Queen, dressed as a member of the League of Assassins, could be taking place within an alternate future and that makes sense for a few reasons.
If Barry returns to the past to save his mother, then he will undoubtedly change the future. That was already proven when he accidentally traveled back in time, and prematurely captured the Weather Wizard; which resulted in new dangers taking his place. This change in the future can give us DC's Flashpoint Paradox. In the comics, this storyline involves Bruce Wayne dying instead of his parents; which results in his mother becoming the Joker, and his dad becoming Batman, Aquaman and Wonderwoman are at war, and Superman is locked away by the Government. The Flash does not have access to those characters but it does have access to Arrow's characters. CW's Flashpoint Paradox could result in Oliver Queen accepting Ra's Al Ghul's offer and becoming the head of The League of Assassins, or my theory, that Oliver Queen becomes the Dark Archer. It would be cool to see Oliver Queen as a bad guy opposed to someone being forced into taking Ra's Al Ghul's position. Either way is irrelevant because the Flash will return to the past to stop himself from saving his mother, and try to set the future back to normal.
Another way Flashpoint Paradox could heavily effect Arrow is the revival of Sara Lance. In the beginning of Arrow's season three the Canary is killed, but Sara Lance is supposedly returning for a big superhero team up! If Sara is dead, then that can not possibly happen. We saw Sara filled with arrows, and then fall from the roof of a building. Laurel, her sister, recovered the body, and we saw the body, lifeless on a table, in the Arrow Cave. She's dead. It's hard to argue otherwise; however if Arrow takes a play from Spider-Man's Brand New Day playbook then she can return. In the comics, when Barry goes back in time to stop himself from saving his mother, he returns to a familiar future, but there are slight changes. New costumes are the most apparent, but also some characters that were dead are revived! Barry's time travel could revive Sara Lance and that would make sense if she is to appear in the forthcoming superhero team up. The problem with this theory however, is that Laurel will no longer be the Black Canary. Sara would have to die again to push Laurel to become the Black Canary, and we would have to sit through her training all over again. That could be brutal or it could be exciting if written right.
The other reason Arrow could take from Brand New Day, is getting his secret identity back. In Arrow's Public Enemy episode, Detective Lance learns of the Arrow's identity and announces it on the news! It's safe to assume news that big was not just broadcasted in Starling City, it probably went national. In Spider-Man's Brand New Day, Spider-Man has made a deal with Mephisto; which lead to Peter and Mary-Jane being divorced, but it also brought characters such as Harry Osborne back from the dead. It also gave Spider-Man his secret identity back. Arrow could use Flashpoint Paradox to give the Arrow his identity back. If Oliver's double life is protected, and Sara Lance is revived, then Detective Lance can smile once again.
If this theory is right, then it's a cop out, and most of season three is pointless. That would be annoying, but Dr. Well's told Barry, and Barry later proved it, "Time is an extremely fragile construct. Any deviation, no matter how small, could result in a cataclysm."If the CW takes this cop out we could be seeing a "cataclysm" on Arrow; which would make the cop out just fine.