Each version of this integration matches a specific build of Unreal Engine 4. Here is what has changed in the Unreal Engine 4.9 release of the integration (in addition to upgrading to the new Unreal build).

Unreal Engine 4.9 - Wwise v2015.1.2

• UI-249 Fixed: Avoid crashing when no Audio Playback device is available on Windows.
• Added a "Spawn AkComponent at location" Blueprint node. See Spawn Ak Component at Location for more information.
• Added support for the Mac Editor.
• Added support for the Mac platform.
• Added support for the iOS platform.
• Added support for the Linux platform.