Supergirl and Flash plan to crossover
It is about damn time too.
From Comic Book.com, (("We are so incredibly excited to announce something that we have dreamed of happening since we starting making Supergirl – The Flash and Supergirl are teaming up!,” said The Flash and Supergirl Executive Producers Greg Berlanti and Andrew Kreisberg. “We want to thank Grant Gustin for making the time to come visit (on top of his already immense workload) and all of the folks at CBS, The CW, Warner Bros. and DC for working this out. And finally thanks to the fans and journalists who have kept asking for this to happen. It is our pleasure and hope to create an episode worthy of everyone's enthusiasm and support.” ))
Now, the bigger question becomes this; Is the Flash/Arrow universe set in the same universe as Supergirl/Superman? Keep in mind that Superman is alive and well in the Supergirl series and is in contact with Supergirl all the time. Superman seems to have been doing his own thing for a while now. There is no mention of a Man of Steel in the Flash/Arrow universe. I kind of hope they do merge the two. However, Flash does have the portals to other universes scattered throughout the city and Flash could end up in Supergirl's universe.
DC Comics TV division is doing everything right.