Reader> [You originally said that Satan and his angels are eternally damned. However consider] Isaiah 65:25, 11:6-10. There are several other scriptural passages indicating God will bring even the ultra-rebel dragon back into loyalty, too.
Me> Let's consider those passages.
Isaiah 65:25 (WEB),
'The wolf and the lamb will feed together, and the lion will eat straw like the ox. Dust will be the serpent’s food. They will not hurt nor destroy in all my holy mountain,' says Yahweh.
The emphasis is this verse seems to be that in the future God's people will be completely safe from all harm. On that we are agreed. However, does the verse promise happiness for the serpent? The Hebrew word for dust, [aphar], can also be translated "garbage." So what is in view here? Is this a happy restoration for the serpent or a humiliating defeat with his mouth full of garbage?
Isaiah 11:6-10 (WEB),
6) The wolf will live with the lamb, and the leopard will lie down with the young goat; The calf, the young lion, and the fattened calf together; and a little child will lead them. 7) The cow and the bear will graze. Their young ones will lie down together. The lion will eat straw like the ox. 8) The nursing child will play near a cobra’s hole, and the weaned child will put his hand on the viper’s den. 9) They will not hurt nor destroy in all my holy mountain; for the earth will be full of the knowledge of Yahweh, as the waters cover the sea. 10) It will happen in that day that the nations will seek the root of Jesse, who stands as a banner of the peoples; and his resting place will be glorious.
Again here is the promise of complete peace in all God's creation, to the degree that vipers are no longer a danger, even for infants. So is this verse simply speaking about vipers or is Satan also in view? The mention of "den" and "nest" suggest that Isaiah is simply talking about vipers in the animal Kingdom rather than Satan himself.
The focus of my studies for the Optimism Out of Control book was and still is God's victorious grace for all mankind, created in God's image, and redeemed at the cross. The observation that the Lake of Fire is prepared for the Devil and his angels, and not prepared for mankind has also been an important point in my arguments. This understanding is critical to understand who is in fact actually sentenced to the Lake of Fire at the Matthew 25:41 Sheep and Goat Judgment.
However, after entering the larger discussion about the extent of God's grace in all creation, I was surprised to learn about the debate over the salvation of Satan himself. Thus I have pursued further study below. As for using Isaiah 11:6-10 and 65:25 for proof that even Satan himself will be saved, it seems like an awkward stretch to me. Depending on these verses to make such a case may do more harm than good concerning the main point. Such a stretched argument may undermine the credibility of the essential point: that Christ is the effective savior of mankind. Christ is explicitly victorious in the redemption of all mankind at the cross, but Isaiah 65:25 certainly is not explicit about Satan.
Please consider these related articles on my website:
For myself, with bold humility I say that Christ must finally save all mankind because he has already proven his intent to do just that at the cross. Actually it is not me saying it, but Christ has committed himself already and proclaimed the good news himself from the cross. Furthermore, he commands us to believe it and give our lives to telling others the good news! This good news is so certain that the main thing that gets him angry now is if we do not believe it and live accordingly.
As for Satan and his angels, I am also certain from God's word that they are sentenced to the Lake of Fire, which is prepared for them for The Ages of The Ages, that is the "The Aion of The Aion," Matthew 25:41 and Revelation 20:10. Can the grace of God bring an end to Satan's damnation for The Ages of The Ages? Certainly! Will he? I do not know.