Let me tell you a little something about Warner Bros and Batman post-The Dark Knight Rises: they have no idea what they're doing. They definitely went after Joseph Gordon-Levitt in a big way to reprise his role as John "Robin" Blake*, but that was before Batman vs Superman became a thing. When Batman vs Superman happened they started putting together a list of guys - mostly in their 30s and up - who they would like to see don the cowl. But all along, according to The Sun, they've been trying to get Christian Bale back, and they've offered him $60 million to return.
The Sun is a tabloid, of course, and 99% of their movie news stories are utter bullshit. But I've heard rumblings that Warner Bros would be willing to back up the money truck to Bale's door, and frankly they would be stupid not to do it. Yes, everybody pays lip service to The Dark Knight Rises closing out Christopher Nolan's Batverse, but why wouldn't you want the star of the biggest Batfilms back for another go?
The studio doesn't want to piss off Nolan - they have gone out of their way to stay in the Nolan business, doing all sorts of deals with Paramount to get a piece of Interstellar - but there's a limit to their kindness, and a billion dollars worldwide could be that limit. A Batman vs Superman that teams up the new Man of Steel with a new Dark Knight could be a hit; one that teams Superman up with Nolan's Batman is a global surefire blockbuster. At what point does all that money outweight the need to kowtow to their creative prince?
In universe it all works as well; the arrival of Superman is surely a big enough event to draw the attention of retired Bruce Wayne. Working from the shadows he would direct Wayne Enterprises to begin working on contingency plans for this alien, and along the way he would discover Kryptonite. It writes itself, and with a 2015 release date Warner Bros clearly is hoping it does.
Will Bale come back? It depends on how much he likes money. There's an honor to letting the character go, but there's also something to be said for the Johnny Depp owning your own private island thing.