Jelly Bean rolling out tomorrow for Nexus S?

Seems so: https://plus.google.com/u/0/108489782256316824947/posts/UvfD6rT3goC

In a post on the Vodafone Australia blog it is mentioned that the roll-out is expected to start at 1pm EST tomorrow. That makes it 4am tomorrow morning here in the UK. This doesn't necessarily mean that the rest of the world will get Jelly Bean at the same time, but it's a likely indicator for when you should be alert for an update.

Source: http://blog.vodafone.com.au/blog/software-update-weekly-wrap-18072012/