In fact, that is a funny thing! Over the last few years desktop applications have moved to the internet, loosing richness but gaining reach. The next move was gaining richness with the introduction of Rich Internet Applications.
By bringing Rich Internet to the desktop, we complete the circle and combine all those things. It adds the availability of local data to the whole thing. Things like this have been there for a bit for a time already, but now these big players like Adobe and Mozilla truly believe in the future of bringing web applications to your desktop, a new era has truly started. And not forget Google Gears.
The future's so bright, I gotta wear shades...
P.S. I'm very curious who will extend the picture above to support these new technologies.