I am not a 100% sure if this is new, I know Google has been testing many variations of @SEMantiks tweeted that Sitelinks now have their own Instant Previews.
Yes, when you go to a sitelink, and hover over it, a preview may show up.
Here is a screen shot, click on it to enlarge:
Is this new?
There is some new discussion around preview tests by Google at UK Business Forums.
Forum discussion at UK Business Forums.
