Similar to Apple switching from UDID to the new Apple Identifier for Advertising (IDFA), the most important changes are the independence from device IDs as a unique identifier (for advertisers) and the introduction of additional user controls (for users). Google issued the following statement concerning the shift:
"To give users better controls and to provide developers with a simple, standard system to continue to monetize their apps, we are replacing Android ID with an anonymous identifier for advertising purposes. This enables users to reset their identifier, or opt out of interest-based ads for Google Play apps." Source: http://marketingland.com/
Google Advertising ID has been rolled out in late 2013 and we've been supporting it since March 2014. However, starting August 1, the Android ID will no longer be supported and usage of the new Advertising ID will be required; this also means that from August 1 on, submission of apps with Android ID will not be possible anymore.
To ensure that all our Android publishers are set for the switch, we've released an updated Android SDK (Version 4.3.0) that removes Android ID usage and supports Google Advertising ID, reflecting Google's requirements.
Learn more about Advertising ID and how to set it up.