There was actually a rumor a while back that Batman might be appearing on the CW shows, but Greg Berlanti shot them down. At least we now know Gotham (and presumably Batman) exists in the Arrowverse, and who knows? Maybe with Geoff Johns co-running the DC movie universe, Batman will be able to come to TV. A fan-favorite choice to play Batman on TV has been Supernatural's Jensen Ackles.
Supergirl premiers Monday, October 10 at 8/7c on The CW starring Melissa Benoist as Kara Zor-El, Tyler Hoechlin as Superman, Lynda Carter as the president, Chris Wood as Mon-El, Sharon Leal as Miss Martian, Katie McGrath as Lena Luthor, Ian Gomez as Snapper Carr, Floriana Lima as Maggie Sawyer, and Frederick Schmidt as Metallo.