Amazon's fork of Android is known as Fire OS, and it ships on all of the company's tablets and TV devices. The current version, Fire OS 5, is getting a bit long in the tooth; it's based on either Lollipop or Marshmallow, depending on the device. Amazon revealed quite a few new products recently, but one announcement flew under the radar - Fire OS 6.0.
According to a developer page on Amazon's site, the update is based on Android 7.1.2, instead of the Android 5.1 or 6.0 that Fire OS 5 used. That's quite the leap in features, and for Fire TV devices, some Android TV abilities like Picture-in-Picture and Content Recording will be included. It's not clear if multi-window will be supported on Fire OS 6, as some OS forks drop the feature (like MIUI), but the post primarily focuses on the improvements for Fire TV devices.
Amazon hasn't revealed much about updating its existing devices, except that all existing Fire TV products will not be updated to Fire OS 6 (at least, for now). These include the Fire TV Stick first/second-generation, Fire TV first/second-generation, and Fire TV Edition. The wording is a bit vauge, as Amazon simply says, "At this time, the previous Fire TV devices will not uplevel to Fire OS 6." That seems to leave the door open for an update in the future, but if so, it won't happen anytime soon.
Fire OS 6.0 will premiere on the 4K Fire TV, which is available for pre-order from Amazon and will ship in October. Hopefully we'll find out more information about v6.0 for Fire tablets soon.
- Amazon developer documentation