BlueZ 5.16 was tagged today and is just coming a little over two weeks since the last release. With this quick release, BlueZ 5.16 is mostly about shipping fixes over BlueZ 5.15.
Fized up in this release are issues with HID over GATT physical location / unique identifier, missing paired property notification, and an endianess issue of long-term key storage. There's also support for storing signature resolving keys and added the Android Bluetooth AVRCP interface.
BlueZ lately has been focusing a lot on improving BlueZ's support for Android -- in part due to large contributions by Intel -- with numerous features.