Assuming for the purposes of this question that series which are yuri or subtext that loop are waiting for one couple to get together, and assuming that stories that don't loop had the one chosen couple get together, which series and which couples spring to mind?

My choices so far:

YuruYuri is waiting on Himawari x Sakurako. Almost without a doubt.
(#2 Ayano x Kyoko #3 Yui x Kyoko)

Virgins Empire is waiting on Ayano x Miyoshi

Love Live! School Idol Project didn't loop
Probably Eli x Nozomi or Hanayo x Rin allowed it to escape
If it ran 2 seasons because it was waiting for the non-loop pair, Maki x Nico

Is Saki looping or simply in a time-slowing bubble of deep gravity? Does it loop individual days instead of years?
If Saki is looping, it probably awaits Nodoka x Saki
#2 is Hisa x Mihoko

K-On! didn't loop (famously)
My guess is that Azusa tried to make it loop waiting for the Azusa x Yui pairing, based on what she said.
But the Mio x Ritsu pairing was simply too powerful for that to work.