Update, 4:54 p.m.: And Zach Snyder made it official during Warner's last Comic-Con presentation. (Seriously, it had a hint of Apple's "...one last thing" shtick.) Snyder confirmed Cavill will be back as Superman and that no Batman is confirmed yet. Snyder said he was searching for something he could show fans that would indicate what the movie (that is still being written, mind you) will be like when it's complete. For that, he brought out Harry Lennix to read this quote, per Slashfilm:
“I want you to remember, Clark, in all the years to come, in all your most private moments, I want you to remember your hand at your throat. I want you to remember the one man who beat you.”
That's from the end of Frank Miller's The Dark Knight Returns, the book that has set the tone for Superman and Batman's relationship for close to thirty years. That little bit of information has comic book fans peeing their pants in anticipation already.
Update, 2:49 p.m.: The Hollywood Reporter says the Superman and Batman combo will kick-off a three year rush in DC comics movies, culminating with the debut of the Justice League. Apparently a Flash movie is slated for 2016 and Justice League will hit theaters in 2017.
Original: The move won't officially announced until the Warner Brothers panel at Comic-Con officially starts, but word has leaked that the long-fabled (and once scrapped) Superman and Batman team-up will be the company's big counter to Marvel's Avengers sequel.