Are you in the preview program? Because there was an update that went out last night for preview members. The patch notes for every update not only states when the update is available, but also gives the day / time when the console will receive the prompt to download that update.
For example:
If your console is in Instant-On mode, it will download and install the update and reboot to standby.
NOTE: Once the update is available, you can manually begin the update by launching the Guide and navigating to All Settings > System > Console info & updates.
If your console hasn’t downloaded and installed the update by 2:00 PM PDT 8/1/2016, you will be prompted to do so at that time.
https://www.reddit.com/r/xboxone/comments/4vj9gi/brad_rossetti_on_twitter_preview_members_prepping/d5ywnw1