Some cool news for Nexus 5 and Nexus 6 owners, the Android M update might arrive on October 5th. According to Telus, the Android 6.0 Marshmallow update for Nexus 5 and Nexus 6 is scheduled on October 5th.
This year on September 29th, Google to announce Nexus 5X and Nexus 6P. The Nexus 5x to manufacture by LG whereas Huawei to hold Nexus 6P. The chances are very less to get an update on October 5th which is just after a week of new Nexus devices would release.
Usually, Google takes some time to release OTA updates for the older Nexus phones. Although you can manually update with factory images and OTA Zip files.