I've been thinking that things like this could mean the "final edition" of D&D: the point at which the edition treadmill is jettisoned for a longer-term strategy.
- E-Books. Your entire D&D library in a Kindle-like device. Wizards sells it to you, and you update it by plugging it into your computer and downloading the most recent updates for the books you've bought. Also can include wireless networking for doing things like sending "secret notes" to individual PC's. Think of the D&D thing like an iPod more than a library.
- Print on Demand. You assemble the books you want to print out from a library of rules that WotC maintains. Subscribe to the service, then you print out exactly the book you need.
- E-Paper. A flexible piece of paper you hold in your hand whose content is delivered via the internet and shown using the "paper" as a display.
- "Sixth Sense" Technology. A wearable/mountable projector that is connected to the internet, that uses whatever surfaces you have available as your "touchscreen."
I think Print On Demand is probably the most feasable idea, though I'm kind of enamored of e-paper as well. E-Books might be problematic for a lot of reasons, and SSTech is still pretty early along (but it's open source, so it would be pretty easy to shepherd it to something awesome for a dedicated team).
What all of these share is that whatever you read the rules off of is updated continuously, but you don't have to be "at a computer" to use them. Computing is becoming ubiquitous, so it would be bizarre for D&D not to use this in the future.
The side benefit of all this is that it also supports
alternate rule systems very well. Imagine a community like Digg for D&D, where we might get official updates, and people also post their rules and house rules, you can "like" the rules you think are great, and integrate them into your own game, perhaps assembling a Print On Demand hardcover that exists
just for your home game. There'd be no need for "4e or Pathfinder" style choices. Wizards could let you do whatever rules you want to do, because they'd control the network.
If WotC controlled the network, they could collect their monthly fees, upgrade the network, come up with new ways to share and distribute rules, etc. One of D&D's strongest assets is the community. Combine supporting the community with an easy way to let players pick the rules they want in their home games, and you might have something that makes D&D mean RPG like Google means internet search.