> It wouldn't be surprise if their Next Goal were to built the Entire ( or Most of ) Browser with Javascript.

Firefox is that already, the UI is XUL (that's one of the reasons why things like Firebug could exist as a plugin, when Chrome and Safari plugins are essentially glorified greasemonkey scripts). But you still need the core engine to run that javascript (and a bunch of other stuff) somehow, and one of the ideas behind Servo is that you could do so with much more concurrency and reactivity than is currently done.