While I agree that Web Services have many advantages to traditional packaged software, there is no reason why newly developed packaged software could not use Web Services.
In my opinion, due to inherent problems in Windows, users are reluctant to install package software on there computers for fear that it would harm their system. When I used Windows I felt that fear.
When I switched to Mac OS X, I suddenly found that it was okay to install as many programs as I wanted on the computer without worrying about problems. This was the way it used to be and it made me realize that much of the emphasis on thin-client systems and web services may be in part due to this installation fear in Windows.
The focus today is to make the browser do everything and the challenge is to make the browser measure up to packaged software.
Web 3.0 may be the emergency of packaged software to utilize web services "instead" of a browser, but this if dependent on Windows Vista giving users the freedom to install programs without fear.