Luis Scott writes in Frustrating GOD: How Open Theism Gets God All Wrong:
Boyd states, “While the Bible portrays the crucifixion as a predestined event, it never suggests that the individuals who participated in this event were predestined to do so or foreknown as doing so.”
Let me make a few comments regarding this quote. First, the Bible does not portray the crucifixion as a predestined event. It clearly states that it was a predestined event (Eph. 1:35; Heb. 9:26; 1 Peter 1:20). Each one of these passages makes reference to God’s plan in Jesus since before the foundation of the world.
Luis Scott. frustrating GOD: How Open Theism Gets God All Wrong (pp. 101-102). WestBowPress. Kindle Edition.
Scott claims the “crucifixion” was a fixed event. His three prooftexts do not mention the “crucifixion” at all:
Eph 1:3 Blessed be the God and Father of our Lord Jesus Christ, who has blessed us with every spiritual blessing in the heavenly places in Christ,
Eph 1:4 just as He chose us in Him before the foundation of the world, that we should be holy and without blame before Him in love,
Eph 1:5 having predestined us to adoption as sons by Jesus Christ to Himself, according to the good pleasure of His will,
In Ephesians 1:3-5, there is a reference to Jesus, foundation of the world, predestination, and adoption. There is nothing about a cross and a specifically Roman form of execution.
Heb 9:26 He then would have had to suffer often since the foundation of the world; but now, once at the end of the ages, He has appeared to put away sin by the sacrifice of Himself.
There is more of the same in Hebrews 9:26. The context of Hebrews 9 at least references “sacrifice” in verse 28. But nothing in this passage suggests anything was “predestined” or mentions anything about a Roman “crucifixion”.
His last prooftext is 1 Peter 1:20:
1Pe 1:20 He indeed was foreordained before the foundation of the world, but was manifest in these last times for you
The question is “what was foreordained?” Was it the crucifixion? Was it a sacrifice? Was it just Jesus as the Messiah? Was it Jesus as mediator? The text does not even mention a “crucifixion”.
Luis Scott is very sloppy when dealing with the text of the Bible. He assumes his position in texts without any evidence. Contrary to Scott’s claims, there is very good evidence that the crucifixion was not a fixed event.
God is Open 
Just had a quick question .Growing up I was taught that Jesus came to die, or in their words he was born to die. Does the Bible or Jesus explicitly say that? Also, if it does, with that line of reasoning, doesn’t that mean that Jesus’ death was a predestined event? ( I am not even remotely a Calvinist, I was just always taught this growing up.)
Here is John Sanders:
Although Scripture attests that the incarnation was planned from the creation of the world, this is not so with the cross. The path of the cross comes about only through God’s interaction with humans in history. Until this moment in history other routes were, perhaps, open.
…
First Peter 1:20 says that God foreknew Christ and thus can be understood as affirming that the cross was foreknown from eternity. But this verse does not necessitate such an interpretation, and so there is no problem for the relational model. All that is required is that the incarnation of the Son was decided on from the beginning as part of the divine project. Ephesians 1:4 says that God chose us in Christ beforehand, and Revelation 17:8 says certain names have been written in a book from the foundation of the world. Again, this is no problem if taken to refer to something like “corporate election,” whereby God elects a course of action and certain conditions by which people will be counted as “in Christ.” According to corporate election it is the group—the body of Christ—that is foreordained from the foundation of the world, not specific individuals selected by God for salvation.25 Moreover, Revelation belongs to an apocalyptic genre that suffers from an overly literal interpretation. Those who believe that everything that happens in the world was fixed (or at least foreknown) prior to the creation need to explain how this comports with names being blotted out of the book of life (Rev 3:5). It would seem that either total foreordination or foreknowledge would exclude the possibility of revising the book. The potential revision of the book seems to indicate that the destiny of these people was not settled in God’s mind from eternity.
Act 2:23 Him, being delivered by the determinate counsel and foreknowledge of God, ye have taken, and by wicked hands have crucified and slain:
Joh_3:14 And as Moses lifted up the serpent in the wilderness, even so must the Son of man be lifted up:
I think what you are saying about the open theory is true but the possibility of the style of death God could have also arranged. Where and how He intervenes in order to accomplish His plans is not revealed explicitly in but a few cases. Even now that I have fully embraced the Open view I think God kind of set the Pharissees ans Sadducees up but NOT that they were not fully cupable.
Acts 2:23 is interesting. I asked Ehrman about this text. He stated he doesn’t think this is about fatalistic determinism. He said it is basically just “everything is going according to plan”. And that is what the verse looks like. “Listen, you killed him. Bad on you. It looks bad, but this is part of the plan. God’s plan wasn’t subverted or undone.”
Sanders, Elseth, and Enyart all talk about how the cross could be subverted. I think Enyart lays out that the plan of sacrifice could have gone down like we see in Genesis 22, a willing sacrifice on an alter. I’ll find the reference.