"The Antichrist may yet be converted to the Gospel."
I find this implausible since the Antichrist's acts, like Judas, are foretold - as is his destiny.
Revelation 19:20
And the beast was taken, and with him the false prophet that wrought miracles before him, with which he deceived them that had received the mark of the beast, and them that worshipped his image. These both were cast alive into a lake of fire burning with brimstone.
Well, this is a work of fiction.
Having said that, prophecy does not exclude human freedom, which I think was the author's thesis, which he handled masterfully. As Judas before him, the Antichrist will freely choose to oppose God and his Christ, thus fulfilling prophecy.
-Theo