Not quite - if you read the HTML5 game performance on iOS 8 blog post, it points out that as of iOS 8 PhoneGap is equally fast to wrappers, but has a lot more features. So you can start using PhoneGap already. And when the WKWebView problem does get fixed, hopefully in a patch soon, you'll get a big performance boost - way above the wrappers - without having to do anything other than rebuild with the latest PhoneGap.
Yeah, i see that phonegap on ios 8 is as fast as ejecta, but theres only a renderer test, what about the phonegap's performance? Have you tried sbperftest with phonegap? Is it's result equals to ejecta?