Executive producer and writer Marc Guggenheim recently spoke with Collider and let the news be known noting it will happen when the time is right.
Well, we’re fanboys and we always fantasize about, “Oh, we could do this cross-over. We could do that episode.” Everything is always on the table. I think it’s one of the things that’s made Arrow special. But we also all collectively feel like The Flash needs to stand on its own two feet, now that it’s gotten its launch from Arrow. I would say, as with all things, we trust our instincts to know when is the right time. Our compass has always just been our gut instinct. When the time is right, it will happen. Greg [Berlanti], Andrew [Kreisberg] and Geoff [Johns] have got to finish The Flash pilot first. There are a bunch of things that have to happen before we can start cross-pollinating shows.
Grant Gustin first appeared in Arrow as Barry Allen with his last appearance seeing the accident that gives him his powers for The Flash.