I agree. I think this viewpoint is a little skewed. Web-based applications have definitely not killed the desktop differences.

However, I think there is a much better chance of them killing the mobile differences to a greater extent, since

1) we don't do as many processing-intense things on mobile platforms, like CAD, designing, etc., and

2) those processing-intense applications we actually do use on phones are also becoming available on the web for the large part.