Of all the Joel articles this one was better than most. As someone else said I see Joel has a very practical kinda guy. He so practical that I don't look to him for setting the future. I've never seen a practical programmer, such as Joel, make anything that is future. I digress. However, his practicality in this article was an interesting slant on the future.
I do believe the next level is making my Google mail work with Flickr or vice versa. Right now all these applications are islands, but there is a lot of benefit to joining them into the larger part. Whatever, that is could be a great thing. Is it just an Web SDK? Is it the real Web OS? It's a practical prediction.