Nobody will rule out the possibility that CBS' upcoming Supergirl series, produced by Arrow and The Flash showrunner Greg Berlanti, will cross over with those two series, which air on the CBS co-owned CW Network.
There are even reports that Berlanti has it built into the language of his contract that such an event is allowed.
The president of CBS, though, is somewhat less bullish on the prospect -- at least right away -- and said as much as the TCAs, according to IGN.
"Well, those two shows are on a different network," Presdent of CBS Nina Tassler said. "So I think we'll keep Supergirl to ourselves for a while."
But chances are that if the shows all continue to do well, the odds seem better that she'd be open to sharing the screen once Supergirl is established.