Spoilers: (Highlight to reveal)
My sources indicate that when BvS opens Batman has existed for close to thirty years, which would place Wayne in his 50s (which is why I expected more grey in Affleck's hair). In this version Batman is still an urban legend, a creature of the night, and no one has ever taken his picture. But he's had plenty of adventures, and the Batcave includes a memorial centered around a tattered Robin costume.

I've heard more, but I'm wary of crossing the line into spoilers. I do quite like this little tidbit, though, because it gives us a sense of a very different Batman than we've ever seen in the movies. This sets Affleck's version apart from Bale and the others easily - he's a quieter operator, not involved in blockbuster battles but in all sorts of badass vigilantism.

By the way, my sources tell me that Wonder Woman has also been in operation for some time before Batman v Superman: Dawn of Justice* begins, and her activities have been just as secretive as Batman's. Her activities were badass as well... but in a very different, and unexpected, way.

Spoilers: (Highlight to reveal)
On the Meet The Movie Press Podcast, guest El Mayimbe from Latino-Review dropped a rumor that Brainiac will be the main villain in the Justice League film, after reportedly appearing in a tease at the end of Batman v Superman: Dawn of Justice. Sources tell Mayimbe that Brainiac picked up the signal from the Kryptonian ship that Superman activates in Man of Steel (which in that movie brought Zod to Earth).

It's worth noting that Brainiac has suddenly become a key player in The New 52 DC Universe, becoming a central presence in Futures End and Superman: Doomed (which tied the character to the pre-New 52 Universe in a typically cosmic/high-concept DC Comics fashion).