First-generation Motorola Moto X is going through a soak test
This soak test could be for a maintenance update designed to prevent the treacherous Stagefright vulnerability from infiltrating the OG Moto X, and taking over control of your camera, microphone and stealing some of your content. We would be flabbergasted, to say the least, if this was for Android 6.0 Marshmallow. After all, the older dual-core chipset in the handset delayed the update to Lollipop. Besides, there are a lot more newer models that should receive Android 6.0 first.
To take part in future soak tests, make sure that you are a member of the Motorola Feedback Network. One condition that they place on those joining is one of confidentiality. You are not allowed to tell the media anything about the tests at all. If you can handle that, and understand that you are assuming a risk by testing a unreleased software build, you can visit the Motorola Owners' Forum to sign up.
Thanks for the tip, David!