Kabookit has word that a recurring character named Felicity Smoak will be a part of the series.
Who is she, you ask?
Well, she's the step mother to Ronnie Raymond. And Ronnie, along with Dr. Stein, comprise the two halves of the Firestorm entity.
So while not specifically saying Firestorm will be on the series, we'll have at least a part of the elements. And that is at least a start.