Recently Stephen Amell of Arrow posted on his Facebook page an old ad for the issue Green Arrow joined the Justice League. There was no explanation. He runs that page personally no one else does it for him. He says so in the videos he posts all the time.
I think it meant something. I think its highly likely he will have a cameo in the next Superman/Batman film to set up a Justice League movie. There is no reason DC could not crossover between its film and tv shows. Arrow has been a very success while other than Man of Steel they are starting over. With the Flash appearing on Arrow this season they now have the foundations to build on to create a universe.