I wonder if the idea to do a Batman/Superman movie was fairly recent. I say this because other than the Wayne Enterprises satellite, which was very subtle, there weren't any hints to Batman in "Man of Steel." The movie didn't even have an additional scene after the credits. I was thinking the other day that a perfect way to set up the next movie would have been to show an after-credits scene where Perry tells Clark that his first assignment is to cover Gotham's vigilante.
I really am looking forward to this next film as well as the proposed Justice League film, but I hope that the plans to feature superhero team-ups don't stop them from making sequels that just revolve around Superman. I think there are still a lot of great Superman stories that have yet to be told in the films, and it would be a shame if we never get to see them.