Today the official IDOLM@STER blog posted this update. There will be a “~14thAanniversary P@rty!!!!!” streamed on Nico next week.
You can watch this live stream on Niconico Live. It will start airing on July 23, 20:00 JST (UTC+9).
Appearing on the stream will be Akabane Kenji (BaneP, CV of 765Pro Producer), Nakamura Eriko (Eriko-sensei, CV of Amami Haruka), Aoki Ruriko (Ruuri, CV of Tada Riina), Watanabe Yui (Yuiton, CV of Watanabe Nao), Terashima Takuma (Terashii, CV of Amagase Touma), and Mineda Mayu (Damayu, CV of Hachimiya Meguru). The IDOLM@STER series producer GamiP (Sakagami Youzou, Hentai) will also appear on the live stream.