I was thinking about "the Teyla plotline" for Season Four and came up with a theory.
Note: I've only seen to the end of Missing, I haven't seen The Seer or This Mortal Coil, so anything that's been stated in those episodes about the state of the Athosians is unknown to me.
it's not about the pregnancy
Most of the fandom discussion of focus regarding "Teyla's storyline" in S4 seems to revolve around her pregnancy and whether the child is going to be 'normal' or a 'miracle baby'. The missing Athosians and her search for them tends to be dropped by the wayside because no-one really cares if primitive peoples go missing or are slaughtered or dying at rates that would horrify us if they were western people anywhere in the world. (I wish I was being sarcastic there, but I'm not: we really don't care - checked out the death/disease rates of Africa lately?)
I'm wondering if the hunt for the Athosians might not turn out to be more important than the fandom thinks it is. After all, "the Teyla storyline" was planned as far back as September last year, when Joe Mallozzi spoke to Rachel Luttrell about giving Teyla an arc in Season 4. And that was long before Rachel Luttrell got pregnant.
So, look at the pregnancy as a part of the story, but not significant to "the Teyla storyline" originally conceived.
the missing Athosians
The missing Athosians are the key: that and the Wraith-worshipper who was left behind as a red-herring. My theory is that the Athosians discovered something that the Wraith didn't want them to find out, and so they were hunted out and seized before they could get the news to Atlantis.
That would tie in the Athosians with the "main storyline" of Atlantis in a way that makes their disappearance and "Teyla's storyline" relevant to the only thing that really matters in the show: the Earth expedition living in the city. As to what they discovered...there's the mysterious fault in the Wraith hives that the Aurora discovered and never got to pass on. There are secrets of reproduction, diseases that could wipe them out, cultural/physiological weak spots, or predators that the Wraith worked out how to minimise or isolate so they wouldn't be a threat - there are all kinds of possibilities for a people who keep their eyes and ears open, who can connect dots, and who could produce someone as practical and learning-oriented as Teyla.
just a theory...with no slapdown
It's only a theory, of course. And it relies on TPTB seeing a bigger picture than they historically have, and using people and characters that they have historically labelled "second-best". Maybe I'm an optimist; but it's more hopeful than some of the alternatives being proposed (mostly by people who dislike Teyla anyway).
One other reason it's possible: I just can't seem to get Joe Mallozzi to give me an answer back about it. So far, I've sent out four emails asking about the relevance of Teyla's missing people and have received not one reply. Which might suggest that it's completely unimportant or more important than he wants to reveal. The thing is, Mallozzi's usually pretty straight-up when I ask him questions that land in the negative and which he doesn't mind revealing. The man will say, "No, sorry, we're not going to do that this year." At the least, he'll say, "You might want to watch [insert episode here]."
Which leaves us wiggle room...or enough rope to hang ourselves on hope.
Either way, it's something to think about.