Waiting for a Flash movie at this point feels, ironically enough, like running a marathon. The Scarlet Speedster's solo film has had a troubled development, one filled with multiple director switches and script rewrites over the span of just a few short years. Though a pair of directors are currently in the process of being locked down (John Francis Daley and Jonathan Goldstein), and production is expected to start on the film once the ink dries, it's almost impossible to believe it's actually going to happen.
Though we know that the plan is for the film to take place after the events of last year's Justice League, story details have been scarce. However, rumors have swirled about which additional characters will show up as the supporting cast to Ezra Miller’s headlining superhero. Most recently, a report surfaced pegging Killer Frost, Heatwave, and Captain Cold as players in the film, with Frost in particular said to be taking on something of a lead role. Eobard Thawne, the Reverse Flash, is also said to possibly be in the film as well, though not as the film’s primary antagonist.
Since the film is being subtitled Flashpoint, it's quite possible that Frost, Heatwave, and Cold will not be the characters that they usually are in the source material. If the film is at all faithful to the 2011 Flashpoint comic, the three of them will likely be heroes, or at least anti-heroes. But the inclusion of all three of them, who currently exist in The CW's popular Arrowverse as well, speaks to a problem that currently hovers over the DC Extended Universe, and it's one that should be dialed back on.
Specifically, the DCEU continually encroaches on the Arrowverse's territory, and not just with those three Flash characters. Deadshot, Katana, Captain Boomerang and Amanda Waller, who all existed in the Arrowverse at one point, had to be killed or written off and had an entire storyline about the show’s Suicide Squad axed to make way for the characters appearing in 2016's Suicide Squad film. (The show even had their own Harley Quinn briefly appear, albeit off-camera, and now she’s disappeared off the face of the Earth.) Deathstroke, a recurring and vital character to the mythology of Arrow specifically, had to be written off the show so he can be in future films and his upcoming solo flick. To Warner Bros., it probably feels like a natural thing to do, because unlike Marvel, the studio actually owns the film rights to all its characters. But instead of being natural, it just comes across as stealing at best, and momentum killing at worst.