According to the rumors on the beacon of truth that is the interwebs, they're apparently going to be a series of movies that cover the Golden Age, Black Swordsman, and the Millennium Falcon arcs. That's 32 volumes of Manga to cover. Miura is up to vol. 35 and starting the Fantasia Arc, where Griffith finally has his own kingdom.
I kinda wonder how bad they'll butcher it. I love Berserk but some of it is kinda...........