According to a Vodafone Australia support page, an Android 7.1.1 OTA update for the Nexus 6P will be rolling out beginning 5PM Australian Eastern Standard Time (3:00PM Malaysian Time) on 6th December 2016. It will be about 650MB in size and you’ll receive a notification once it is ready to download.
The Android update will be pushed in stages where 10,000 phones will be selected at random for the first 3 days. Subsequently, 10% of the remaining devices per day will get it and it should be rolled out completely in 2 weeks time. There’s no mention of the Nexus 5X but it could be receiving the same update beginning next week as well. It’s also unlikely that it will get Google Assistance since it is exclusive to Google Pixel handsets.
The new Android 7.1 is an incremental update to the original 7.0 Nougat. It has a new shortcuts feature which is kinda similar to Apple’s 3D Touch feature on the app icons. The icons are now circular like on the Pixel and the keyboard gets a GIF support as well.