The Nvidia Shield Tablet K1 will be updated towards Android 6.0, the over the air update will bring the OS to Android 6.0 Marshmallow. The update update package is not yet available as standalone download though.
Nvidia meanwhile posted the release notes on their website. The update will being new features like Now on tap and better energy consumption in standby mode. Nvidia also includes a new feature called adoptable storage, users can use a micro-sd card as part of the system internal memory. The internal storage of the K1 is max 32GB.
The release notes also make mention of a new interface for the camera-app and a configurable settings menu, also optimization of Nvidia delivered apps is new. The download is a whopping 665MB. Again this is the K1 model, not the slightly older Nvidia Shield Tablet.
Nvidia Shield Tablet K1 gets update towards Android 6.0
