Supergirl
When Clark is investigating the ship under the ice, he notices a pod with a dead body in it, and then sees a pod that is open, with no body inside. So obviously someone opened up that pod and was able to escape, but just who was it?
Well one pick that definitely makes sense is Supergirl. Warner is definitely going to want to bring in some strong female heroes moving forward, and just Wonder Woman isn’t going to cut it, especially when it comes to dealing with that complex backstory. If DC is to introduce a character like Supergirl, who shares a relatively similar backstory as Superman, that means less time can be spent explaining.
Another thing that makes Supergirl seem likely is the digital comic that comes with a pre-order of the Man Of Steel Blu-ray. That comic details the origin of Kara Zor-El aka Supergirl. While her appearance in the comic by no means ensures she’ll show up in a future movie, it sure does make it seem a lot more likely.