Batman vs Superman : Dawn Of Justice
Also, Warner Bros has released the official logo of the film (on the left). With such a name, we can more or less conclude that it will be a prelude to the Justice League movie franchise. I think Marvel's will pay close attention to the development of this project as it is head to head competition to their successful Avengers franchise.
No official plot details has been shared yet but we already know that Batman (Ben Affleck), Superman (Henry Cavill), Wonder Woman (Gal Gadot), and Cyborg (Ray Fisher) will in part of the project.
Personally, I quite like the movie title, what about you?