If we do as many fans do, and just stick "The Circle" at the end of the second season as a nice tidy ending where both the Marshalls and Enik find their way home, then the only person left in the land with any understanding of the technology would be the Zarn. What might he do to the place (which would still have a few nice characters in it like Cha-Ka, Dopey, and S'Latch) if there's no one to stop him? For that matter, even if the Zarn doesn't make trouble, what will happen the next time a pylon breaks down if there's no one to fix it? Perhaps we can rest easy knowing that at least Holly will find her way back with a working knowledge of the pylons some day as Ranee.
On the other hand, if we take the episode order at face value and figure that, from season 2 on, we're watching temporal duplicates of our heroes, then can they ever really "return" to an Earth that already has a set of Marshalls in it? When Rick got home, did he find another Rick there, living his life? To avoid headaches, maybe we should just assume that there is an entire divergent Earth corresponding to the divergent Marshalls, so they can have some real hope of getting home after all.
Ranee's last words to Holly in "Elsewhen" imply both good and bad things to come. On the one hand, she implies the family will eventually escape (heck, "The Circle" comes just two episodes later); but she also makes a cryptic comment that Holly needs to cherish Rick and Will because they won't always be there for her... which could mean something ominous (maybe they die) or not (maybe they're just all separated for a while). Holly certainly does lose her father at the start of the third season.
