You could say that but htere are hits that she is back from hiatus or slowly starting to come back.
But most likely it is because side M has to stand up against other male idol games that dominate the market at the moment like Idolish7, marginal#4, tsukiuta and many more which got anime adaptations last/this year. It is more likely that the anime coming so soon is a marketing strategy to stay relevant inside this huge pool of male idols which have a pretty big fanbase.
Wow. But I really hope Risa, or Tane-chan, goes back. I loved her as Kaori in Shigatsu wa Kimi no Uso, so...I'm excited!