At the moment this should be treated as a rumour that's likely to turn out to be false, but it's worth mentioning just in case there's some truth in it somewhere. If it is true, it's also a bit of a SPOILER, so if you don't want to know, stop reading now.
With Paradise Lost getting delayed (and possibly cancelled) Bradley Cooper is rumored to have joined the Superman: Man of Steel cast for a very intriguing cameo role. However while Comic Book News says it's happening, it hasn't been confirmed (or denied).
According to this new rumour, Cooper is coming in to play Lex Luthor. The villain is known to have been in early versions of the Man Of Steel scripts, but was removed, leaving General Zob as the main bad guy. Now it's being said that he'll turning up briefly in the movie, setting up Lex to be a major player in any sequels.
As mentioned, treat this as rumour for now, but it could be quite cool if it does happen.