Here's virtual reality technologies as they will look in ten to fifteen years:
Instead of glasses, you'll be wearing contact lenses. They will either contain a small camera, or you'll be wearing one around your head. They'll be connected to a computer that's small enough to be worn all the time, with power life hopefully being more than a day so that it can be worn continuously and charge while you sleep. The camera will allow whatever program you use to tell where your head is at any given time, track where you are in the physical world, and track various real world objects. The contact lenses will ideally be able to track where you're eyes are looking at any given moment so that various optical effects can be recreated.
The most obvious (and to my mind, most boring) application of these lenses will be full immersion virtual reality. You still won't be able to touch or smell anything, as those technologies come later, but you would be able to put yourself inside a movie, or given enough physical space, put yourself inside a game with virtual things to shoot at. This is probably the first direction for the technology to go, because it means that very few objects need to be real world tracked, if any.
The less obvious application is overlaying virtual things onto physical things. If you pick up a blank book, the lenses can project words onto your retinas so that to you the book looks like Moby Dick, Pride and Prejudice, or whatever else you feel like reading. Your physical bookshelf would just need one book, while your virtual bookshelf would be able to hold every book ever printed.
Similarly, you could replace your television with a virtual television. It would be projected onto your eyes by the contacts in such a way so that it would seem like the screen was being projected onto a wall in your house. The obvious advantages (besides cost) are being able to move it wherever you want to, having it be invisible to people who don't want to watch it, and even muting it if you have the sound coming in through micro-headphones instead of installed.
Another example; you could replace your computer with a virtual computer. As you'd be running this all on a lightweight computer anyway (with a power about 100-fold of what we have today), it makes a lot of sense to take the typical user interface of monitor+mouse+keyboard and remove it from the computer entirely. What this means is that you would have your lenses project a keyboard onto any flat surface and a monitor projected into the air above it. Most of this, like on today's desktops, would be done without you really knowing how it happens - to you, it would just look like you had given substance to a computer by sitting down at a table. Input could be done in a number of ways; either you would wear a ring on each finger so that they could feed information back to the computer, or you could coordinate with the camera (which would mean you have to keep your fingers in at least peripheral vision when you type). To use the "mouse" you would just slide a finger or two across the table.
But this brings up an interesting point - if I could have a computer interface be represented by almost anything, with cost not being an issue because it's all virtual, why would I choose it to be represented by a keyboard and monitor? Why wouldn't I choose to view virtual files in some novel way, like having my e-mails stacked on top of my desk, or having my photos exist in some virtual photo album, or having a virtual phonograph that played all my music? All these virtual items would be available to you at any time you wanted them, because your computer would travel with you wherever you went.
The virtual television would be a fine solution for viewing legacy media, but once the technology to do a virtual overlay exists, full immersion would likely merge with the movies. At the most basic level, you could do something like the old movies of the '50s with red and blue glasses. It would be more realistic of course, because it would have more information, and because it wouldn't be bound by the screen. The advances in videogame technology would likewise be immense, but the same problem that's happening now will still be happening then; the quality of media can't match the advances in technology.
Next time - practical applications of the virtual overlay in advertising, marketing, and informatics.