10.0.0 Version of google play services clint libraries as well as the firebase clint libraries for android will be the last version of these librariesthat are supported by Android API level 9. i.e Android 2.3, Gingerbread.
10.2.0 will be the next version, it will increase the minimum supported level from 9 to 14. This change will happen next year 2017.
Reason for Discontinuing use of Gingerbread and honeycomb in google play services:
Gingerbread is an old platform, it is almost 6 year old. So most of the android developers are not using this platform inm there apps.
So discontinuing use of this will enhance the capability and help android developers to make better aaps. By this we will be able to provide better collection of tools with the greater speed.
How it will affect to make Android app:
If you will use 10.0.0 Google play services and fire base it will work with ginger bread same as earlier it was. But when you will use the upgraded version of 10.2.0 and your app is supporting API level 14 or above than you will not face any version proble and if your app is supporting lower API level than 14, then you will face the version problem. while building the app.
Target of this course:
It is a course of action to discontinuing the support of API level that will no longer able to receive the Google play Services updates, If you update your app with API level 14 and publish it , than those devices which support less than that API level (API level 14) will no longer able to download or see the update. But now a days few android devices are using less than API level14. Most of the devices are using API level 14 or above that.