I mean I always imagined the series ending more so with Guts and his party slowly gaining strength and there's a final showdown between Guts's party and the God Hand.
They defeat the God Hand, but at the cost of some people getting severely wounded and Guts finally defeats Griffith.
I personally think the ending will be positive to contrast the overall negative vibe of the series at the moment....
But that's just wishful thinking I suppose.
Who knows what will happen?
Personally I think Casca will go with Griffith, and Guts is probably going to end up with Farnese, and he's going to witness Casca get killed by Griffith, this is going to trigger Guts's rage and he's going to brutally kill Griffith.
That's my personal prediction long-term.