According to a Nikkei article a Morning Musume event will be the first event to be broadcasted by TBS in 3D.
Since 3D seems to be the main focus of entertainment right now it was expected that we would see it eventually in some way in Morning Musume, and since they have already had a chance to use 3D (at a runway event) it seemed a bit more likely that they would try it out someday soon.
The article cuts off at the middle so we can’t read the entire article but it does give us a generally good idea of what to expect, but hopefully more details are released soon.
The date seems to be on 8/25 according to 2ch.
Source – hello-sayunii