It would also appear to be ne expergisci possint, "lest they be able to awake." Expergisci is deponent, meaning that it is "to awake" not "to be awoken."
I have not heard the "auroram videre potes" proposal before, but that makes sense. I was thrown off by her accentuation of the last syllable of that line and the separation between the syllables, making it seem like a separate word, and by the strong lack of aspiration of that final s, but it does make sense. Listening to this track really does confirm that.
I would say that nunquam extinguunt is a separate sentence. That is:
Tellus dormit, et liberi ignem (I do think this is ignem, not in diem; in diem is "into the day" which makes little sense) faciunt. Nunquam extinguunt, ne expergisci possint.
"The Earth sleeps, and the children make a fire. They never extinguish it, so that they cannot awake."
The pronunciation with "ne expergisci possint" is clouded by the fact that she (accurately, by classical rules) elides ne and expergisci, and so the "k" part of the "x" in expergisci seems to separate from the word itself, seeming to create "nec" and then a second word.
I also think "mane" is in fact "manet", making it "the time of awakening remains."
Even in this track I cannot seem to get the words to the "ehem" line. "Ehem desperatione" doesn't seem right to me; "Behold! you can see the dawn in desperation" just doesn't seem to fit.
I really wish Square Enix would release the official lyrics to this and/or find a singer who actually knows how to pronounce the words (she follows neither classical nor ecclesiastical pronunciation).