It looks like Warner is the loser in the staring contest with Marvel over the May 6, 2016 date.
Warner has just announced that Batman V Superman: Dawn of Justice will be moving up nearly two months to March 26, 2016. That’s pretty far away from Marvel’s May release date for Captain America 3. With both movies previously holding that date, it was only a matter of time before someone moved.
With the strength Marvel has coming off Guardians of the Galaxy, it’s not surprising that Warner is the one to budge.