It will come in 2017.
NBCUniversal has revealed in a Video that a second season of Starmyu is in the works. Besides that 2 OVAs are being worked on, both of them will release later this year (July 27 and September 21).
The first seasonw as Streamed by Funimation, which describes the story as follows:
“Ayana Academy: home of musical dreams and insane competition. New student Yuta Hoshitani dreams of being in show business, but to get there he’ll have to gain acceptance from the Kao Kai (Cherry Blossom Flower Association), Ayana Academy’s three highest ranking students. For Yuta and his friends to get into the music department, they’ll have to get into the Star Frame class, which is taught by the Kao Kai members. Though the newcomers are struggling, they catch the interest of one of the Kao Kai members, which just might send them on the starlit journey they’ve been dreaming of!”
Via: Anime News Network