When I studied Virtual Reality Development @ NYU with the turn of the century, I always assumed that when computing power and functionality got up to speed, we would greatly benefit from reproducing certain real-world interfaces in 3d virtual worlds to the betterment of the human-computer interface.
As generations are becoming wired at younger and younger ages, I'm realizing that by the time really useful virtual reality will exist, there will be few if any classical "real world" metaphors left to implement in any 3d virtual human-computer interface.
There won't really even be computers by then.
When immersive realtime three-dimensional experience becomes a substitute for the world around us, augmented reality will have been the norm for a long time, and beyond that, we will have more intimate ways of relating to data than desks, pens, paper, ink, folders, and file cabinets could ever have provided.
In short, I'm starting to visualize the unimaginable future awaiting my grandchildren, and it's excitingly full of wonder. I'm not so much worried about what they'll miss out on, as I am worried about the metaphors I'm going to miss out on.
(Inspired by this piece from ReadWriteWeb)