Traditionally, Google has first released the source code for a new Android version in AOSP and followed it with an OTA update for Google-managed devices, later posted the factory images of the same on dev website.
So, the first part is done. Now, the wait starts for the OTA update, which seems like should be coming to Nexus 4, Galaxy Nexus, Nexus 7 and Nexus 10 devices in the coming days.
What is new in Android 4.2.1_r1.2
- Reduce the power consumption in off-mode charging
- Allow device to sleep in off-mode charging
- Do not suspend when disconnecting from charger
- Charger: suspend enable in charger mode
We are expecting to see the OTA in the coming days, followed by Android 4.2.2, which should be arriving in a month or so.