That's similar to what some companies have done with Apple's AirPlay: Added wireless capabilities to easily stream music from a mobile device.
Indeed some of the Google Cast partners have long supported AirPlay: Harmon Kardon is one that comes to mind. Over the next few months, you'll see speakers from it and Sony, LG, B&O Play, Onkyo, Philips, Pioneer and Raumfield that support streaming audio.
Google is essentially sharing the technology it has built into its own Chromecast and Chromecast Audio products with these hardware partners.
The latter device recently gained support for multi-room audio sync: You can play the same tunes on multiple speakers around the house with it. Later this year, Google Cast speakers will get the same feature so you can mix and match speaker brands for different rooms as you see fit.
As far as Android TV integration, that's now new. However, there will be a wider range of television brands joining the ranks: Look for TV sets with Android TV from Arcelik, Vestel, RCA, Hisense, TCL and Bang & Olufson. Currently, you can buy a set from Sony, Sharp or Philips with Android TV.
Noticeably absent is Samsung, but that makes sense since it uses its own Tizen platform for Smart TV functions and services.
The move towards wider Android TV support makes me wonder if 2016 will see Google add 4K video support for Google Play Movies and TV shows.
While standard HDTV sets make up the bulk of sales today, the prices of 4K televisions continue to drop quickly while at the same time, 4K content availability is on the rise.
Big names such as Amazon and Netflix already offer enough content for my 4K set to watch the higher resolution programming a few times per week. And just around the corner we'll see new 4K Blu-Ray media players and discs to bring even more content.
I wouldn't be surprised to see Google soon jump on the 4K bandwagon, particularly when low-cost rival options such as Amazon's FireTV already support it.