As far as I can tell Google has not said anything officially yet, though as this gains more publicity it may push up their time table. Google's search results may soon be so instant you do not even have to switch over the the linked page for what ever you are looking for.
"SEO Consultant Patrick Altoft first noticed the feature, saying that they appear to be full-page previews with some interesting highlighting by Google.
One of the fascinating things about this is that they are highlighting certain sections of the page in orange and expanding the text to provide a snippet of information. This shows that they have the technology to know exactly where a piece of text is on every single web page. The snippets highlighted are not always the same as the snippet in the search results.
While it certainly seems like a great feature for users, we have to wonder what the effect on advertising and pageviews will be. Another big question is, just how real-time are these preview results? If we're seeing a search result for a dynamic page, are we getting a real-time preview or a look at a cached version from minutes, hours or even days ago?"