Some interesting scriptures to consider:
1 Samuel 15:29
And also the Strength of Israel will not lie nor repent: for he [is] not a man, that he should repent.
Psalms 135:14
For the LORD will judge his people, and he will repent himself concerning his servants.
Jeremiah 26:13
Therefore now amend your ways and your doings, and obey the voice of the LORD your God; and the LORD will repent him of the evil that he hath pronounced against you.
Interesting scriptures! One thought... It appears that repentance appears to be the key here to God changing his mind.
Consider Manassah and how wicked he was, but when he truly repented, God changed his mind about his punishment, and instead of judgment in his day, Manassah's children received his punishment.