Sprint-based Galaxy Nexus smartphones are now receiving their Android 4.2 Jelly Bean (JOP40D) updates, hosted by Google. There's been no word on over-the-air (OTA) updates just yet.
Instead of waiting for the OTA update, there's always the option to manually download the update and install it with more than one method provided on the Galaxy Nexus forums across the world. The update is around 100MB, which you can grab here. The download is direct from Google, so you know it hasn't been tampered with.