I can see that happening for major websites but I think personal websites or ones made by only a small group might not be able to do that. Maybe in the future there will be pre-made apps where all you need to do is enter the domain and add branding and maybe change themes, sort of like how Wordpress works, only it's for an app and the site owner something pre-made on their end to send to the app.
The drawback to this situation is there won't be any web surfing.
100% agree with you. The bugs & exploits for such platform would be incredibly disruptive.
But let's be honest, the web isn't going to die out any time soon. The world isn't black & white. It's here to say for at least the next 10-15 years. After that point, I'm not so sure...