-The fallout of "Flash’s" second season finale, referred to as Flashpoint, will have an effect on the other shared universe CW/DC shows. "Flash" lead Grant Gustin even said that he knows of a Flashpoint change in "Arrow," which he said was a subtle one.
-When we pick up with "The Flash" in the season three premiere, a year will have passed since Barry altered the timeline and he will be loving his new life. Both of his parents are alive, Wally West is the Flash, and Barry works for the CCPD. But Barry will also get advice from another speedster about navigating the new timeline, Gustin said.
-Joe West’s relationship with the rest of the cast will have changed as well. While he will interact with Kid Flash, he won’t know that the hero is his son, Wally. And since he didn’t raise Barry Allen, the two won't be terribly close -- therefore, Joe won’t know who Cisco (Carlos Valdes) or Caitlin (Danielle Panabaker) are.
-New cast addition Tom Felton spoke about his character, fellow Central City Police CSI Julian Dorn, saying that he will be suspicious of Barry Allen and will have a "slightly abrasive" relationship with him. He also said that while Julian will know Barry through years of working together, Barry will not be familiar with Julian due to his newness in the Flashpoint timeline.
-With "Supergirl" now on the CW, Grant Gustin expressed great excitement at the thought of Superman coming to the series (played by Tyler Hoechlin). But don’t expect to see a Flash and Superman team-up anytime soon. Gustin revealed that he has not yet shared a scene with Hoechlin, and doesn’t know if he actually will.