Today, Google "stopped updates to Google Play services for Android Lollipop devices." Android 5.0 became stable in November 2014, with Lollipop accounting for less than 1% of active devices.
The first version of Material Design for Android was introduced, followed by version 5.1 Lollipop in March 2015. Even though Android phones and tablets don't receive monthly operating system updates or security patches, they do receive new versions of Google Play Services, the backend services that power many unique features like backups, two-factor authentication, and other capabilities for app developers. Google will stop updating the version of Play Services for Android if there is little activity on the device account. Currently, Lollipop (API levels 21 and 22) is at less than 1%. Dropping support will allow the company to focus on devices with more powerful hardware and newer operating systems that support the latest features.
With the end of these updates, Android Lollipop devices will continue to work, but "will not receive any new features, significant security updates, and may not be compatible with some apps" that rely on Google services. Last July, Play Services ended support for Android 4.4 KitKat. Updates to Google Play services are currently available for Android 6.0 (API level 23) or higher.