In general I think future editions will keep looking at what is happening in popular culture, technology and game design around it, just like they tried to do this time. But that is a boring answer. Lets try to have a bit of fun instead.
I think future D&D will come in the shape of database structured ebooks, where some patches are free, others are included in subscriptions and the rest will have to be bought.
The publishers of these rules will learn to make use of the things that this kind of design opens up, and it will be possible to choose a subset of the rules depending on play style. A DM will be able to create encounters, maps and NPCs on the fly, having set parameters beforehand. I expect some sort of handheld ebook reader to be the standard interface used, unless people can be bothered to bring their laptop.
Support will exist for bluetoothing (or something similar) from the devices/laptops to the home telly, which will then be used as gametable.
When all of this is announced, there will be a huge outcry on the Internet as many people feel that the game designers have cheated them all these years, selling them books, dice, miniatures and tiles - and now making them all obsolete. Others will say that it is now impossible to roleplay, as all the gadgets do is help combat. A third group will demand to get all the software for free, as it doesn't cost anything to let many have it than just a few.
And then there will be those who claim that this is nothing new. This is how they have been gaming for over 30 years, and they are glad that the designers have finally caught up. The possibly biggest group of all will be people who will support the new ideas because they are new, in many cases without even knowing how the new things will work.