According to the Film Distributor’s Association, the upcoming Batman v. Superman film will premiere in the United Kingdom on April 29 of 2016, which is one week before the film’s May 6th United States premiere, or rather, which is one week before the worldwide release of Captain America 3.
Some may find this news to be shocking, and may wonder why the US won’t get their Batman/Superman fix first, before other international areas do. Marvel has a tendency to release their films early via overseas markets (i.e. Captain America: Winter Soldier’s UK release on March 28, 2014, followed by its US release on April 4), and, perhaps, financial reasons may motivate such a tendency; what might such tendencies towards film release imply about popular American cinema, America’s place in the film industry, and superhero films, particularly if a film with such an eponymous title as Captain America: Winter Soldier is not released in the United States before being released in Britain? Regardless, such decisions are not arbitrary in nature, since such films are supported by millions of dollars, and are expected to produce profit of millions more. Additionally, you might consider the following question: would an early release of Batman v. Superman allow for financial dominance over competitor-superhero-films like Captain America 3?
Despite the early release for Batman v. Superman, there does not seem to be any evidence that the premiere date was changed in order to avoid conflict with the third Captain America film.
Sources:Film Distributors Association, Comic Book, Forbes