Apple though not a champion of open source or open standards, with iOS 8 it has become both. It has also introduced significant improvements for application developers who hope to exploit new API will need to work around a bug that breaks a common way for loading local files from the device.
Besides, here a few more benchmarks that sets IOS 8 a potential leader to be a huge win for hybrid apps.
HTML5 Support Level Test
The HTML5Test.com benchmark reveals that there are some APIs that are only available in WKWebView- a very supportive to iOS 8 version.
Webgl Is Now Enabled
WebGL was a hidden feature in iOS 7 but starting in iOS 8, it is officially supported in both WKWebView and UIWebView. This is huge for developers who require native-level 3D animation capability, especially for game app developers
Improvements to CSS3 Capabilities
iOS 8 has implemented many more CSS3 features than iOS 7
The most notable change is that WKWebView now has a mechanism to communicate between the native layer and the browser layer. For example, Cordova utilizes internal AJAX an IFRAME element to pass the data. WKWebView provides a direct way to send data between the layers. It will be much more accurate and take much less overhead compared to the UIWebView way of sending messages.
In a nutshell, all HTML5-based hybrid apps will run much quicker and become more stable for iOS devices with the new the new WKWebView engine. Playing a bigger and bigger role in application development...a lot of games and apps can be seen in future.