More Vocaloid3 is coming. And yes, her name is MAYU and she was recently announced by EXIT TUNES in one of their live events, "EXIT TUNES ACADEMY" a few days ago.
Her character design is done by Hidari. You feel familiar with her design? It's because Hidari already made some illustrations for EXIT TUNES albums and Hidari also provided character design for FRACTALE and Natsuiro Kiseki.
According to her appearance (and some tweets mentioning her) she will be a yandere girl (just look carefully, she's holding an axe back there). And her rabbit plushie also got a name, it's Usano Mimi.
She also has an official site here.
About her voice, a video had been uploaded during the live event but later deleted by the developer. Later, EXIT TUNES stated an apology that said that currently MAYU's voice is being developed and doesn't really exists. You can find a demo at YouTube though.
Please note that currently MAYU's voice bank is still being developed so her voice that you are hearing is not the end result.