I didn't realize they killed chromecast audio. Pretty frustrating. I may not have committed so much to their echosystem in Dec.
Disclaimer: I work at Google, but don't have insider knowledge on this.
It seems like Google really can't handle long term support of anything that isn't wildly successful (200+ million users), and even for those things that hit said benchmark, long term support is bumpy, inconsistent and unpredictable.