johnsmith - note the non-webview Cocoon platforms have been deprecated for a long time now so have not been supported for some time. I don't know if that's what you're using?
Anyways, it turns out there's another obscure property we can rely on to detect WKWebView. Apparently Cordova detects it the same way, so if iOS 11 breaks it, it will break all Cordova apps, not just our own Hopefully that is good enough for the future. So the next build actually brings back the "enable WKWebView" and "use new Intel XDK project format" options. I still strongly recommend using WKWebView where possible, since it is significantly faster!