Isn't the browser going to become the definitive cross platform, cross browser host for future apps with HTML5?
For the user to get to the browser they first see the desktop. On the desktop is a tiny icon that says "browser". The remainder of the space is taken by apps the platform provider has placed there. To buy a book or video game and download it to your tablet you can open the browser and navigate to amazon. Or enter directly into the desktop app that takes up a 1/4 of the screen space and is customized for the particular user's use.