The LA Times reports CW president Mark Pedowitz stated there are no plans for additional series at the Television Critics Association press tour.
"There is no intention, at this point, to spin anything else off," Pedowitz said.
It's also learned that The CW passed on Supergirl, which went to CBS, as The CW was intent on increasing their male viewership, which is why they decided to go with The Flash. The CW was actually approached with Supergirl before The Flash, but the article notes The CW didn't want to "commit to another superhero series because it would detract from its overall mission to broaden out."
While Supergirl is on another network, it's created by the same team behind Arrow and The Flash; Pedowitz did note the three series will have cross-promotions, and Pedowitz also noted the possibility for a Supergirl/Arrow/Flash crossover is there.
"We’re open to crossovers," Pedowitz said. "It’s [EP Greg Berlanti's] call because he understands his shows."