While Barry Allen is dealing with the consequences of changing the timeline on The Flash, the rest of the Arrow-verse hasn't been clued in on Flashpoint just yet. The biggest non-Flash related change is that Diggle's daughter Sara no longer exists and was replaced with his son. Diggle hasn't yet learned this, but the reveal is coming. Actor David Ramsey has opened up about how Diggle will feel about the change, and how it will affect his relationship with Barry moving forward.
Much more compassionately than you might think. Diggle can't miss anything he's never had and 'Flashpoint' changes history -- it changes his history directly -- so he never can really miss Baby Sara anymore, because he never had her, but he is concerned about Barry. Barry's actions were reckless, and with all that power, being reckless -- to someone as disciplined as Diggle -- comes as a shock.
At Heroes & Villains Fan Fest (via ComicBook), David Ramsey was asked (as he has been for a few months now) how Diggle will react to the news that he had a daughter in a different timeline. Everyone figured that Barry was in for a reckoning from Diggle, but the drama lies in Barry's ability to even change timelines, not what was actually changed. You can't miss something you never had, and while fans might still miss baby Sara, this Diggle has only ever had a son.
For those not up to speed on The Flash, Flashpoint is an alternate timeline that Barry Allen created when he traveled back in time to stop his mother's murder. And when he traveled back in time again to let the event play out, the timeline he returned to still featured some drastic changes to his friends and family. One of these changes was that Diggle now had a son named John Jr. instead of a daughter, and Barry is the only one who remembers what things used to be like.
Diggle just forgiving Barry isn't good drama though, and Diggle taking major issue with what Barry did makes sense. Diggle has always been flabberghasted by superpowers, and the idea that someone has the ability to change history on a whim probably won't sit comfortably with him. While I think that the ripple effect of Flashpoint is wildly over exaggerated (Diggle is the only non-Flash character to even be affected by it), at least the Arrow-verse can make good use out of Barry's selfish use of his powers. You know you've messed up when Diggle hits you with one of his patented lectures.
It's more than likely that Diggle and Barry will have their confrontation during the Heroes vs Aliens crossover, which begins Monday 28 at 8 p.m. ET with Supergirl and then continues throughout the rest of the week on The Flash, Arrow, and Legends of Tomorrow.