DC Films Presents: Dawn of the Justice League host Kevin Smith has revealed that the door is open at Warner Bros. for some sort of crossover between their big and small screen adaptations...There's been a lot of controversy over Warner Bros.' decision to keep their film and TV DC Comics adaptations separate, and as disappointing as it may be to some that Stephen Amell's Green Arrow won't show up in Justice League, it's something which also has its advantages in terms of the creative freedom the driving forces behind these projects have.
Regardless, Kevin Smith revealed on his Fat Man on Batman podcast (via CBR) that he agrees with fans who believe that Grant Gustin is worthy of playing The Flash on the big screen, indicating in the process that his version of the Scarlet Speedster could very well meet up with Ezra Miller's. "We did a piece where we talked about -- I don’t know how much I’m supposed to say because they cut it out," Smith said of the recent DC Films Presents: Dawn of the Justice League special. "But the idea [came up] of, 'Hey man, DC is known for nothing if not a multiverse,' so at which point I was like [to Johns], 'Could they [frick]ing crossover?' And he was like, 'Ahh.' So doors are being left open and stuff like that."
While nothing is confirmed at this stage, the filmmaker went on to accurately point out the advantages of a crossover: "Think about this, you can have Ezra Miller be the Flash and you could also have Grant be the Flash, because there’s a multiverse at work."
If this happens, it's probably a very long way off.