It's slightly more complex than that. Google has made an effort to make Chrome the default browser going forward. However this will only affect Jelly Bean (and to a lesser extent ICS as it is an optional install there).

However I believe that apps still have to use the built in rendering engine when using the WebView control.

I'm not sure whether this is a strategic or technical decision from Google but I suspect the latter. Changing the WebView engine would have a major effect on compatibility for existing apps.