Flash and Arrow have both set record rating numbers for the CW this Season. Another Show appears to be in the wings based on that success.
Let us not forget that Supergirl and Titans are both in development as well. And I would like to point out that DC has said that everything on TV is in a shared Universe.
I envision that Supergirl, Titans, Arrow, and The Flash will cross over once all the shows establish themselves.
Lest we forget The Flash, Constantine, Gotham, and Arrow all have other DC Superheroes appearing in their shows.
Some are showing up in their before they become heroes (i.e.....Montoya, Allen, Palmer, and Corrigan).
Others sound like them may show up as heroes such as Firestorm.
We shall have to wait and see.
More as the TV Season Progresses.
To Be Continued......
Go forth and do well.