According to Sprint’s support forums, the Galaxy Nexus is getting Android 4.3 today. The build is JRO03U.L700GJ04. No other details were provided, but it should happen before long. Obviously, this is for the Sprint model only and not the Verizon variant.
This is the first update the Sprint G-Nex has had since January of this year. That update was to Android 4.2.1.
Things are happening!