Here's something to consider about the next-gen of consoles; how much better can graphics really get?
And I mean on a practical level here.
From where I'm sitting, I get the feeling that the next gen will most likely be defined by improved network connections, advanced social interaction and online streaming (like OnLive, etc). There may also be more of a focus on improved and enhanced user interfaces, and more of a focus on designing the perfect 'home entertainment' system that does everything (including making your tea) and less on designing a machine that's solely intended for playing games. Basically the improvements will be in what's considered right now to be the boring back-stage stuff.
In terms of graphics, the improvement curve is starting to plateau now, and I'm not entirely convinced it's because of current gen limitations. For the next generations of games, there may be a slight bump up in the visuals and audio, as seen in the Wii-U, but I'm skeptical that it will be as much of a leap as it was between - say - the PS2 and PS3.
Remember, if it's still extremely expensive to make an A+ game to current-gen specs at the end of the current cycle, imagine how much more money developers and publishers would have to sink into a next-gen game if everything has to be near-to-photorealistic.
The industry just won't be able to sustain that, especially in this day and age.
One of the reasons why the Wii became the surprise seller this generation was because Sony and Microsoft were basically stuck in a glorified dick-swinging contest over who had the best graphics. Seriously, the E3 conference where they unveiled their new consoles, Sony and Microsoft should have just brought out two Jeremy Clarksons to duel over who could scream "POWER!!!!" the loudest.
It reached a point that still stands to this day; there's very little difference in what the PS3 and Xbox 360 have to offer, which doesn't really leave much by way of choice between the two. Really, if you're going to buy one, you may as well just decide on the flip of a coin.
The Wii, however, wisely chose to distance itself from that schoolyard war and focus on providing a new user interface that was easy to sell and exciting at the time (still is, in my humble opinion, when it's done right). That's how it won over so many wallets; it set itself apart from its competitors (I know, that's business 101 stuff, but it still needs to be said).
The Wii-U's a tougher sell, and frankly Nintendo haven't been doing a very good job at it, but I do think the gamepad controller is enough of an innovation to see the console at least do a lot better in the long run when people fully "get it", so to speak.
I wouldn't necessarily call the gamepad a game-changer in the way motion controls have been, but it does have the potential for more practical uses in and outside of the gaming world than its naysayers claim.
The tl:dr version: in my humble opinion, the next generation may not be defined by power, but more by the difference in player experience.
As it stands right now, and as Jim Sterling has already pointed out on this very website, the Wii-U kind of has the edge on that right now.