After missing chance after chance, Infinite Stratos 2 finally delivers in sudden and surprising fashion when Tatenashi spins around in her shower stall during the eighth episode. Episode twelve brought some R-rated changes as well.
The nudity in this series adds an already towering number of nude service anime from the 2013 fall season. As was recently mentioned in the comments, there was some surprising nudity from Noucome and some TV airing nudity from Magi 2nd season*. This raises the nipple-sighting count for the Fall 2013 season all the way up to nine shows. As best I can tell, it is the most ever for a single season of TV series.
Keep in mind that a 13th episode of IS2 is slated for later this year. The OVA capstone episode for the original Infinite Stratos contained nudity, so it seems a decent bet this one could as well. Once it is out, there will probably be enough material at that point to consider a two-season Infinite Stratos video.
A random side note, one of the nipples was actually visible on the censored TBS broadcast version, though you have to use a lot of effects to just barely see it.
*Technically the Magi nudity occurs during the second cour which aired during the Winter 2014 season, though it’s all part of the same “season” of Magi so I’m counting it. There’s also this scene during the first cour which has good chance of adding something on blu-ray.