Right now, there's nothing that can be considered as crazyness-inducing as the Wii back in 2006 (just talking about "pure" gaming consoles; otherwise, iOS and Android ARE the next big thing). 3D is not the next big thing at all, Gamepad + Miiverse neither, and certainly TVTVTVTVTVTVTVTV won't either.
I believe it's going to be something...software, not hardware. And it would be a consequence of all this recent social focus, thinking about it. Let me explain.
Social and Internet made far, far easier for people expressing their opinions on everything (especially things they don't know a thing about XD ), but it also allowed so many people to express their hobbies, or better...their talents. YouTube, Facebook, Twitter...are all full of photos/videos of people showing off their biggest abilities: how many videos of people playing piano/guitar/any instrument are on the web? What about people singing? And what about reviews/let's play/any possible video content, even short movies?
It's easy to see the impact of social in giving to people the possibility to show what they can do. But we haven't seen this in gaming yet. Or better, not in its biggest form possible: so far, just sharing gameplay videos/photos (which is still great, no doubt). And this is the reasoning that leads me to thinking that the next big thing in gaming is going to be...a game where you create your own game.
I already have many ideas about this software.
First of all, its basic tools should be very, very easy to use for creating games: 2D tools for stages, characters with a little editor, objects, and these are available once you play this software for the first time.
Then, the software should have an in-game store where you can buy other tools, through in-game currency, system coins (like the 3DS ones) or real money. Some of these tools should be also randomly distributed through free downloadable content some months later from their appearance in the in-game store (like SpotPass content).
Once completed, this games could be distibuted just through people in your friend list, or on the digital store itself (a specific section of the whole DD store of the console, called "The house of people's games", or something similar XD), where they can be downloaded by everyone with a console. In the latter case, they should be first approved by the platform holder itself, obviously (and before that, users should see the official terms for distributing content on the digital store, and agreeing with them).
When distributed publicly, games can be priced too: users should have the possibility to put them with no cost or at 0.99 as minimum, all depending by the amount of effort (and money of any kind spent).
The more these titles succed both sales wise and reception wise, the more in game money you earn, money that can be spent in the in-game store.
Another big feature of this title should be a sort of Gold Membership: paying a fee per month (between 1.99 and 2.99), users would have access to many more and better tools, especially for creating (and animating) your own character. But people who have games that sold a fixed amount on copies on the digital store could have access to the Gold Membership for free for a limited time(from 6 months to a year, depending on the amount of success).
Moreover, the games that sold huge amounts could be put outside of the specific users content channel and being highlighted like "User content of the month", for example, for gaining more revelance.
Multiplayer could be possible too, especially for Gold Members: it would allow people to create teams for their games (one doing levels, one doing music, and so on), with a fixed high amount of team members. Still, making a game all alone should be possible without problems.
The only big hurdle I can think of for this idea is the economic aspect: how could people obtain to gain from the games released without being worried of seeing their own money stolen? I thought that something like a sort of PayPal specific for the people who uses the software and releases titles on the worldwide marketplace could work: users should just use their account for registering on the official site of the software (where anyone can see the latest titles released even without entering the digital shop on the console), and they'd have a personal bank linked to their credit card / PayPal account, but it should be always the user deciding when the money can pass from the site's "personal bank" to its real life funds, every time. Obviously, releasing content on the marketplace should be available just for who is 18+ years old: children and teens can share the content created between each other.
I think THIS could be what's going to capture people's imagination in the future: a software where everyone can create a game, of any scope, from the littlest to titles with a good amount of work behind. The choice is up to the player.