Preview at WWDC likely in June, followed by September launch.
Mac OS X Lion's Safari is Snappier and More Stable Thanks to WebKit2
Starting in Mac OS X Lion, we've learned that Apple has started utilizing WebKit2 in their Safari web browser. The advanced version of Apple's Webkit engine was first announced in April of 2010. WebKit2 is described as a new API layer for WebKit that offers both speed and security improvements:
Google's Chrome browser introduced a similar sandboxing model when it was introduced.