We'll see. No doubt it will do well but the summer (and whole year) is overstuffed with movies; they will have to time it right (and make it decent) if they want to get the repeat viewings that make a box office success. Avengers will be the bench mark.
Yup, 2015 is going to be a crazy summer for blockbusters. Avengers 2, Jurassic Park 4, Star Wars Episode VII, Terminator 5, Pirates of the Caribbean 5, Independence Day 2.
But Superman v Batman is going to capture the imagination more than any IMO. Won't necessarily do the most business, but the two characters are truly iconic.
Personally I hope it remains, first and foremost, a Superman film. I don't think they'll be able to resist a full-blown Superman/Batman film though, and expect Bats to get the same amount of focus as Supes.
I'm hoping it's a smaller film than Man of Steel. Let the characters sell it. Batman, who is early in his career and still operating in the shadows, comes to Metropolis to investigate Superman. Maybe gets help from Lex Luthor, who is beloved by the people of the city. Sees Luthor as a kindred spirit, a billionaire who wants the best for his city. And obviously, as the story goes on, Batman discovers that it's Luthor who is the villain and he and Supes team up to stop whatever dastardly plot Luthor has come up with. Need a fight between Superman and Batman, so kryptonite will have to make an appearance. Maybe have someone like Metallo as Lex's muscle, but I don't think we need any Batman villains. Save that for his solo film, which I'd guess will happen in 2018.
As for how to portray Batman, I hope they go a bit more comic-booky than Nolan. Wouldn't mind them using the Arkham universe Batman as inspiration.