Google will soon stop updating Play services for phones running Android Jelly Bean – this covers all three versions, 4.1, 4.2 and 4.3 (API version 16 to 18, respectively). The lifeline has not yet been cut, the JB phones will receive a final update with version 21.30.99, which is scheduled for release at the end of August.
Jelly Bean was first announced in 2012, nine years ago. It brought major improvements such as Project Butter, which made the user interface smooth (with vsync at 60 Hz). Other major additions include Google Now, the now outdated Android Beam, extensible notifications, and the ability to disable notifications from individual apps, as well as a number of audio enhancements (AAC support, non-disruptive playback, multichannel audio, USB audio for external DAC).
Android Jelly Bean features: Google Now • Expandable notifications with buttons • Account switching
Android 4.2 arrived later that year, 4.3 arrived in 2013, both kept the name Jelly Bean. The three versions of JB account for less than 1% of active Android devices and Google is not convinced that they are actually used. Anyway, it will end support for these versions of Android, which will lighten the load on its development team (older versions require a lot of special case management).
App developers are encouraged to drop support for Jelly Bean as well. If they configure their apps to target API version 19+ (Android 4.4 KitKat), JB phones will still be able to install older versions of the app, but they won’t see new versions.
However, if an app has a significant part of its user base that is still on JB, developers can download multiple APKs from the Play Store so that even Android 4.1-4.3 devices can continue to receive app updates.
For more details, see the Android Developer Blog.