A huge rumor is hitting the internet tonight which is getting DC fans geared up for a possible appearance of Supergirl in the upcoming Man of Steel sequel.
Apparently, Geoff Johns and Zack Snyder had been privately working on a script for the follow up to the Superman reboot before Snyder took his leave of absence. This little tidbit comes in the wake of Wonder Woman being a massive blockbuster hit for the DCEU. With the universe looking to continually expand and introduce new characters into their thriving cinematic lineup, she might be the next one to get the solo treatment.
The source from 4chan claims that they'd been developing the sequel and are planning on Brainiac being the main villain with Supergirl intersecting in the story. Again, this is just rumor and speculation at this point. Obviously, they would recast the role and would not use Melissa Benoist as the tv and film worlds are totally separate entities.