Not only that, but those animals safely dwelling and nesting in the land of burning pitch and brimstone that shall not be quenched night or day with smoke going up forever, will also possess it forever from generation to generation. 
(Sonia is referring to the whole sequence of chapter 34: it’s kind of hilarious how verse 11 right after verse 10 starts talking about the animals safely living there and raising their young thanks to God.)
In fact, 35:1, continuing the same prophecy, talks about how the desert, even in Arabah, will rejoice and blossom and be glad. Edom is part of the Arabah region, as is made clear (among other places) later in chapter 35:6-7 when it talks about Arabah in language similar to Edom’s destruction but in reverse; the land is healed for jackals to live in it safely, and then becomes a highway for people to travel through! (And redeemed people, too, not wicked people. In fact the whole thing is about rebel Israel being saved from pagan oppression, once rebel Israel has been utterly ruined for their sins, and having their eyes opened and their ears unstopped by YHWH’s salvation on their behalf.)
So, yeah, at least one of those forevers isn’t quite forever. 
You are right though…Aion is so hard to nail down anyway. And while it’s important to the argument, it’s not really going to be the card I lead with…Thanks. Sass