The fact that they've made it a mystery makes me think that it is going to be at least a bit of a big deal, i.e. a newer film. So X-Men DOFP is a big possibility seeing as a French version has been announced recently... Let's just hope they come up with some better artwork (although I doubt they will). Although Ant-Man and Fantastic Four are both out soon, I'd say it's still too early to announce them. Yes the Age of Ultron steelbook was announced before its release but that was about a week before, not a month before. I also doubt it will be Iron Man 3 or GOTG as Zavvi already released a steelbook for that and they don't seem to re-release steelbooks that they have already done, but rather steelbooks that they missed out on the first time round, e.g. Thor. Whilst something different like The Incredible Hulk or Daredevil would be the best route to go, it will probably just be X-Men. I hope i am wrong though!