Wonder how God would react if Satan confessed his sin and said that he was sorry. Pretty sure that is not going to happen though.
I actually think this is a legitimate line of thinking, Our God's character is a Gracious God, A Merciful God, a Loving God, its Who He Is, we understand the Character and personality traits of God, and He can't be any different. Part of the reason we can totally trust Him is that He's a fair and Just God.
So it would be God of different Characteristics if He was not gracious and merciful to all of His creation.
To me when Cain was doing wrong God warned him to do what was right, or he would end up succumbing to sin.
To when Satan was doing wrong God also sent numerous warnings to him, to do what is right or he would end up succumbing to sin.
God sent Isaiah to the king of Babylon, and warned Satan, what he will do if he keeps walking in sin.
Isaiah said to him "you have said in your heart (heart)( because he actually hasn't done it yet" I will ascend into heaven, I will exact my throne above the stars of God, I will be like the most High"
Also we can read in Daniel, about the king rebuked and chastened being made into a beast and to eat grass.
Also in Daniel it was prophesied as future that Satan will ascend into heaven and throw some of the stars down to earth. As explained in more detail in Revelation a third of them.
Dan 8:9-10 And out of one of them came forth a little horn, which waxed exceeding great, toward the south, and toward the east, and toward the pleasant land. And it waxed great, even to the host of heaven; and it cast down some of the host and of the stars to the ground, and stamped upon them.
To me Satan is a numbskull, God told him what he would do if he didn't buck his ideas up, and like Cain he kept on rollin.
To me there is a time when the door of forgiveness closes but that is more dependent on the person than on God, once someone understands the truth and see's God has a plausible and legal redemptive plan, and they then still make a conscious decision to reject Jesus Christ then they have committed an unpardonable sin is how I see it.
Heb 10:26-27 For if we sin wilfully after that we have received the knowledge of the truth, there remaineth no more sacrifice for sins, But a certain fearful looking for of judgment and fiery indignation, which shall devour the adversaries.
Those who accept the Word of God and trust God have now received eternal life.
To me once God left heaven, and became flesh and dwelt amongst us, Satan had a bout of severe indignation and ascended into heaven, was opposed by Michael and his cohorts, and himself along with a third of the host were cast down to earth.
And the Lord saw Satan fall as lightning from heaven.
what about after his fall?
Satan is a defeated humiliated and powerless being, just like the other fallen angels, as per the gospel accounts.
He will be used by God in the future and only as a tool to bring about events like the judgement's on the earth in the tribulation as God has planned, so to me he eventually made his choice and is a rejecter of God and His Word, and The Savior His only begotten Son Jesus Christ .