When Android M was officially announced, Google gave the bad news that the Nexus 4, Nexus 10, and Nexus 7 (2012) were not to receive the update due to the age of the devices, but that may be about to change.
A reference to the codename of the Nexus 10, manta, appeared in the AOSP repository for the device and an update dated May 28th was found marked as android-m-preview. Similar updates were found for the Nexus 4, and Nexus 7 WiFi, lending suggestion that those devices may actually receive the updated Android operating system.
It seems that Google is still investing in the older devices with the Android M rollout, which is great news for adopters of the Nexus devices, because that’s what the Nexus programme is all about. Whilst there’s no official announcements for the support of these devices, don’t be surprised if that changes closer to Android M’s public release.