The biggest problem for Sekirei is that the manga is still ongoing. Here's what Aroduc had to say:

<zaitcev> Sekirei likes creepy pre-OP sequences.
<zaitcev> In ep.01, who the heck was the baby? Little Musubi?
<Aroduc> Prepare to find out... NEVER
<Aroduc> 7Arcs appears to be rolling this one for the long haul.
<zaitcev> But... 13 episodes?
<Aroduc> Which is alright with me I guess, though it'd be nice if they had a conclusion to this season instead of... well... obviously not.
<Aroduc> Not even 13
<zaitcev> I'm disappointed.
<Aroduc> The manga purists are happy.
<Aroduc> "Rarr rarr, nothing changed."
<zaitcev> Those damn losers.
<Aroduc> Me... I wish there was a plot or something.
<Aroduc> Instead of some random characters spawned in the eleventh hour as a flimsy excuse to fight some character none of them have met before.
<Aroduc> Not to mention all the others lurking around in the background that they won't meet nor have anything done with them.
<Aroduc> "Come back next year for season 2 to find out all these answers! Oh boy!"
<Aroduc> Meanwhile, 7Arcs is cashing in on the Nanohamobile with that stupid movie.

While following manga slavishly pleases the carry-over segment, it does not make me confident that creators of the anime are capable of making up a satisfactory ending before manga itself ends.