No, you don't need to publish the app again. The published app contains a wrapper with the PhoneGap plugins that you have enabled. Everything else comes from the server, so once you redeploy to the cloud, you're all set.
You only need to republish if you add any new Phonegap plugin. For example, when you add PushNotifications and Phonegap needs a plugin to operate on that. Other than that, you don't need to republish. The app will check whether or not you have created a new deployment for your app and will download the new components.