In fact some Nexus S owners claimed their devices are already updated with Jelly Bean, thus it's all about time for all the Nexus S to get latest Android version very soon. May be tomorrow at your country time.
Because Vodafone said their company will be starting the update rollout tomorrow at 1 pm in Australia time, while SFR it's reported to deploy the update today.
If we take their claims, then we are expecting the Jelly Bean will make its way to all Nexus S across the earth in the next few days. Therefore just wait.