Steven Frank has a ponder on the state of UI metaphors and the obsolescence of the desktop. He contends that the real innovation is happening on mobile devices, with fewer standard conventions:

The benefit of pinch-to-zoom over previous zooming methods is so immediately apparent that it justifies the learning curve. That the learning curve is extremely small also helps. I find it fascinating that a huge portion of iPhone usability training is done via the TV ads, pre-sale. They’re both marketing and instruction.

And back to the desktop:

And this seems to me to be the barrier to moving forward to any sort of next generation of computer interface, whatever it might be. Numerous projects (Squeak comes to mind) have put forth ideas as to how we might interact with data in the future. As amazingly revolutionary and beneficial as your new idea may be, you can’t escape this albatross of legacy data.

Filesystems may come, but good, new metaphors seem to be few.