According to this document the folks over at SprintFeed got their hands on (Sure looks like the ol' Sprint Playbook), Nexus S 4G users should expect an update to start rolling out July 11. The update includes a couple fixes from Google, namely enabling a secure setting for NFC and TTY support (ASAP!), but the stuff most are looking for seems to be baked in as well -- fixes to Wifi and 4G data signal strength and changes to the PRL download mechanism and configuration.
The OTA should roll out over a four-day period starting July 11, and all devices should have received the OTA by July 14. Of course the manual download location will probably get leaked soon after the roll out begins, and if so we'll let you know.