“Satan saw that his disguise was torn away. His administration was laid open before the unfallen angels and before the heavenly universe. He had revealed himself as a murderer. By shedding the blood of the Son of God, he had uprooted himself from the sympathies of the heavenly beings. The last link of sympathy between Satan and the heavenly world was broken.
Yet Satan was not then destroyed. The angels did not even then understand all that was involved in the great controversy. The principles at stake were to be more fully revealed. And for the sake of man, Satan’s existence must be continued. Man as well as angels must see the contrast between the Prince of light and the prince of darkness. He must choose whom he will serve.”
Desire of Ages p. 761

“By the power of His love, through obedience, fallen man, a worm of the dust, is to be transformed, fitted to be a member of the heavenly family, a companion through eternal ages of God and Christ and the holy angels. Heaven will triumph, for the vacancies made by the fall of Satan and his host will be filled by the redeemed of the Lord.”
The Truth About Angels p. 287