You can get URL for a newly requested Webpage by “navigationAction.request.URL” in decidePolicyForNavigationAction delegate method.
func webView(webView: WKWebView, decidePolicyForNavigationAction navigationAction: WKNavigationAction, decisionHandler: (WKNavigationActionPolicy) -> Void) {
if let urlStr = navigationAction.request.URL?.absoluteString{
//urlStr is what you want, I guess.
}
decisionHandler(.Allow)
}