4. Batman/Superman/Wonder Woman: Trinity
Given that Batman is going to be introduced in a Superman sequel, what better way to introduce Wonder Woman than by having her join the already established pair in a future movie for a storyline that's ready made for the trio?
Batman/Superman/Wonder Woman: Trinity establishes the first team-up between the world's finest trinity: Batman, Superman and Wonder Woman. The trio are thrown together when one of Batman's greatest enemies, Ra's al Ghul, recruits Bizarro (a Superman villain) and the Amazon warrior Artemis (a one-time Wonder Woman villain turned heroine) to aid him in his plan to create worldwide chaos. Whilst also having to fend off a global villainous threat, the trio also clash with each other - given their different philosophies - which adds an interesting sub-plot to the main story and would follow seamlessly on from the Superman/Batman crossover movie in which the heroes are set to fight each other. It's an excellent story and, given that the villainous trio amass an army to invade Themyscira, it would make for an epic big screen spectacle that would expand the geography of the DC cinematic universe in a similar way Marvel did with
Thor.