No Soul Left Behind?

I was talking to Joe Luna today and brought up this idea I had about the devil. I had been thinking about this for a while: will Satan ultimately be redeemed? I can't imagine God as a hypocrite (love your enemy, right?), so certainly His love extends to the adversary, but has God written the Devil off, or does His elaborate plan ultimately bring Satan to salvation in Christ, setting free all the imprisoned souls in the process? I'd like to write a book about that! I hope I didn't give away His secret!