Latest Chromebook device that were announced at CES 2017 are running Chrome OS 55, with Android subsystem based on Android 6.0 Marshmallow. Google is now working on a new Chrome OS update that will pack Android 7.1, which will bring a few new features.
The update will also make it easier to view and interact with multiple Android apps at the same time. The exact roll out date is unknown, but it should be out in late January. Thanks To Chrome Unboxed, we have first confirmation that Android 7.1 development for Chrome OS is really happening.