Absolutely not. As greenyoda said, there are things that web browsers just can't do, such as gain access to the file system or to certain OS APIs that aren't available in a browser. Sure, there may be a trending movement towards SaaS for a lot of apps (SaaS is super hip), but not every app can go that route.
thanks for the links! All very interesting and it's kind of reassuring to know I was not the only one worrying about this (and the general positive attitude)