Android 2.3 Gingerbread, according to Google, still runs on approximately 1.3% of devices hitting the Play Store every month. But with Google Play Services 10.0.x, Google is placing an end-marker for the OS's support of the Play Services package going forward, which signals what is essentially the final death of the platform as far as Google is concerned. When Play Services 10.2 arrives, it will leave behind Android's crunchiest iteration.
Google Play services 10.0.x is the final release that includes full support for Android version 2.3.x (Gingerbread). Apps developed using future SDK releases after 10.0.x will not be able to connect to Google Play services on Android Gingerbread devices.
This means that while Gingerbread devices will still have Play Services functionality on the v10.0.x GMS packages going forward, apps built with the SDK after Play Services 10.2 launches will see GMS functionality fail on Android 2.3. In order to keep support for Gingerbread, a separate APK built on the older SDK would have to be created (or an older one maintained, as the case may be).
Loss of GMS support is pretty much the end of the line for an Android version these days. And given Gingerbread was launched nearly five years ago, it's probably safe to pull the plug. We'll miss you, Gingerbread... I guess.
There's a much more detailed post on the Android Developers Blog about this news, which also apparently includes the deprecation of Honeycomb. That means the oldest version of Android with GMS support is - or rather, will be - 4.0, Ice Cream Sandwich.
- Google Developers