Okin said:I admit that Guts may not want to kill Griffith upon this revelation, but that doesn't mean he has forgiven him.
You may have misunderstood me, I don't think Guts would forgive Griffith. The complication of the Demon Child being a part of Griffith, imo, would only further fuel Guts hatred for Griffith. And as you stated, the presence of the Demon Child could easily result in Guts hesitating to kill Griffith along with whatever complication Casca's influence would promote. The beast would also become a factor in how the conflict is resolved.
Though off topic, I also think that Sk's words before the Moonlight Child incident might be of significance. Something along the lines of "what you want may not be what she wants" this could actually pertain to the child. The obvious conflict being Guts desire to kill Griffith and Casca's motherly nature to protect her child. Though Guts new found curiosity towards the child and his dream about the beast are also major factors that must be considered.
Given all these factors, forgiveness is the least likely scenario. To the point of being next to impossible.
Edited for relevance.