In addition to Idoling 10gou, Maia Kobayashi, the identities of three more new members have been revealed.
Idoling 11gou - Suzuka Morita (森田涼花)
Suzuka is a 15 year old girl from Kyoto. Her talent agency is Horipro Osaka, and she is a member of their idol group, Hop Club. Coincidentally (or not), Idoling!!! already has a member from Horipro Osaka, who is also a member of Hop Club--Mira Takiguchi. More than likely, we'll see and hear a lot about the senpai-kouhai relationship between the two when the new members join the show in April.
Idoling 13gou - Serina Nagano (長野せりな)
Source (accessible only by i-mode enabled cell phones)
Serina is a 13 year old girl from Chiba. Some may know her as one of the Oha Girls from the popular children's show, OhaSuta. On the day of the announcement of Idoling!!!'s new members, Serina's graduation from OhaSuta was also announced. Her talent agency is Box Corporation, the same as two current Idoling!!! members: Mai Endou and Erica Tonooka.
Idoling 15gou - Nao Asahi (朝日奈央)
Nao is a 13 year old girl from Saitama. She is currently a model for the Japanese fashion magazine, Love Berry. It is unclear on how Idoling!!! will affect her work with Love Berry, but many of the current Idoling!!! members do work outside of Idoling!!!, so Nao will more than likely be able to do both at the same time. Her talent agency is Vision Factory, which is a first for the group.
Information about Maia Kobayashi and the rest of the new members has not surfaced, yet.