About Android 6.0 Previews

Our devices will not get Android M. Everyone's saying it.
So what is this? Why google worked on these devices for Android 6.0?

android-m-preview
- Nexus 10
- Nexus 7 (2012)
- Nexus 4

android-m-preview-1
- Nexus 10
- Nexus 7 (2012)
- Nexus 4

android-m-preview-2
- Nexus 10
- Nexus 7 (2012)
- Nexus 4

Quote:

On October 15, 2014, Google officially announced that Android L would be known as Android 5.0 "Lollipop". The company also unveiled launch devices for Android 5.0—​including Motorola's Nexus 6 and HTC's Nexus 9—​for release on November 3, 2014. Google stated that Nexus (including the Nexus 4, 5, 7, and 10) and Google Play edition devices would receive updates to Lollipop "in the coming weeks"; one more developer preview build for Nexus devices and the new SDK revision for application developers would be released on October 17, 2014. Update schedules for third-party Android devices may vary by manufacturer. https://en.wikipedia.org/wiki/Android_Lollipop

Maybe we need to wait a little bit.