(I know I'm going off on a tangent here, but bear with me)
However, I think this will be a mistake on Casca's part. I've had this theory for the final battle of Berserk for a while now...
After this chapter, it's certain that Griffith will become king - perhaps not just of Midland, but the whole world. In all purposes, Griffith has not just achieved his dream, he's gone far beyond it. But I think Griffith still won't be satisfied. Something will keep gnawing at him and he might ask the other members of the God-Hand for advice for what it is. Then it'll be revealed that Griffith is still not satisfied because he's incomplete: the ceremony of the Eclipse wasn't entirely right because Guts and Casca (people marked for sacrifice by the Brand) didn't die. The God-Hand will reveal to Griffith that the only way he'll ever feel at peace is if he finishes the job that he started back at the Eclipse by sacrificing the original Band of the Hawk.
Meanwhile, Casca will come back to him and despite the hesitancy he feels in his body (because her and Guts's son is part of him), Griffith kills her. He then sends the Apostles to fetch him Guts. Somehow, Guts learns of Casca's death (perhaps Griffith even boasts of killing her in order to provoke Guts into seeking him out) and completely snaps. Griffith's final act of treachery re-awakens all of Guts's rage and his desire for vengeance.
Guts initially goes out alone, slaughtering every Apostle that gets in his way, but is eventually overwhelmed by all of Griffith's forces sent to capture him. At this point, Guts's friends return to save him and once they realise they can't stop him from his goal, they help him gain entrance to Falconia. Thanks to their efforts, Guts gets in, kills everything in his path and finally faces Griffith.
How their final duel would play out, I have no idea. But I'm certain something like this will happen near the end of the series. Lately, Guts has only thought of protecting Casca and his friends - something big needs to happen to make Guts snap and seek out Griffith again, thereby bringing the series full circle.