Maybe since Henry is the author, he will somehow be able to disperse the dark one immortality while still destroying the power, and it will be able to save him from his death curse problem. I do think that Henry being the author is probably still important. They keep talking about it.
I really am not sure i think how this happens is all that important. I think Henry is probably the guardian. Henry will be saved from the death curse he is under. Rumpel will rid himself of the dark one power. The immortality will not be passed. There will be some dialogue about it that will work it all out in some way that will make me roll my eyes.