Zack Snyder said that Batman v Superman will not be based on The Dark Knight Returns, but will be influenced by it. Superman at the end of Man of Steel has been established as a strong ally of the US government. In DK Returns, this was also the case, and the US government ordered Superman to take down Batman, a rogue vigilante. So the next film could work with an older and wiser Batman in his 40s, who, thus far has eluded arrest... Or a younger Batman, Cavill's age, who has just burst onto the scene. I have no idea who the villain will be that causes Batman and Superman to join forces together, but I don't see it being Lex Luthor just yet... I wonder could brainiac make an appearance?