^ It's an MoS sequel, therefore making it a Superman film. It's just not SOLELY a Superman film.
Based on what we've been told, it's basically Warner Bros.' version of X-Men: Days of Future Past, which is both a direct sequel to First Class AND a sequel to X-Men, X2, and X-Men: The Last Stand.
It is a MoS sequel in the same way Iron Man 3 is an Avengers sequel. The MoS events have a large influence on it and it takes place after MoS, but it is not a Superman film by any means. It is a Batman/Superman film. This is not a Superman film guest starring Batman in the same way Iron Man 2 was an Iron Man film guest starring Black Widow.