So Kevin Smith has been trying to bring his Green Arrow villain, Onomatopoeia, to Arrow. But in an interview with Den of Geek he revealed he will be returning to direct on episode of The Flash. In the interview, he said:
“I know I’m going back to 'The Flash,' first week of September, to direct Episode 7 of Season 3. Still haven’t heard anything back from 'Arrow.' You know, I wish, it would be amazing because I would love to write and direct Onomatopoeia in the show. Um, but I know they’re doing — what is it? — Wild Dog this year, as well as Vigilante, so maybe they’re just like ‘we don’t need you,’ or whatever. But, at the moment, anyone over there raises a flag; I’m like ‘please, let me in!’ That’d be fun as f***.”
So while he still isn't going to direct an episode of Arrow, he will be directing the seventh episode of The Flash Season 3.
I personally hope that Kevin Smith makes it to Arrow to direct an episode, based on how Season 4 went, but who knows, maybe Season 5 will actually be good. Because of what was said about Arrow "returning to its roots." But still, it would be pretty cool to have him direct an episode of Arrow.