I would assume that, as with most Google things, it gets rolled out in a 24-48 hour time span. Disclaimer: No source for this, but that's how it tends to go, if memory serves me right.

Edit: Maybe comments on the post by [+Eddie Kessler](https://plus.google.com/111742562190411471360/posts/eGL4JeDM...) will reveal more (they do not at the time of writing).