Or Android intents, whereby applications can intercept particular URL schemes to e.g. play Youtube videos in the app rather than in the browser.

misses the point by a mile.

web and native will eventually merge to the point that for most intents and purposes the user can't distinguish between them. It'll never be perfect, but it'll be "good enough", that whether an app comes from the web or from the HD, the user won't really notice except perhaps in the initial startup time, and probably not even then (everyone expects to "install" an app).