According to Reggie Fils-Aime the next generation of consoles has started, and Wii U is the first one to the party. To Nintendo, next gen seems to be a combination of new and interesting tech and the creativity to take advantage of that tech. To some it's the promise of a high ceiling that no other console can achieve. To others it's better graphics and better effects that promise to immerse you in these experiences that much more. The answer of course is a bit of all of the above, but in the Wii U's case, its such an interesting and unique piece of hardware that people are having a hard time nailing down exactly what it is.
The Wii U is a next generation console.
(yes, for your information I do know using a period and then using the term period was redundant, but please indulge me)
Regardless of hardware specs and what it can do 5 years down the line, the Wii U is the first new kid on the block, and while he might not end up being the last one standing in this contest his presence alone signifies the start of a new cycle, and a new generation of hardware.
Now, I say all this as someone who has always been a bit jaded when it comes to Nintendo. I was a Sega kid, and to this day adore and cherish my memories of the Genesis & Dreamcast. Ironically, the Dreamcast was also a system that was high on creativity and horsepower until it was eclipsed by the other consoles of that generation. I can say the above statement because I'm able to discern the difference between something that is not of quality and something that is just not for me, and the Wii U falls within the latter category. It's an impressive bit of tech to be sure, and we will see if that can overcome some of its weaknesses. Its competitors however are not the PS3 or the Xbox 360. The Wii U's foes haven't even entered the arena yet, so its difficult to justify the argument that it's not next gen when its main competition is. I will critique a lot of what the Wii U has to offer, but I won't backhand it by saying it doesn't deserve to be in the conversation.
I might not be a fan of Nintendo's newest project (and if you listened to my podcast rants in the past you know for a fact that I'm not), but I try and give credit where credit is due. They beat everybody else to the punch. Now we'll just have to wait and see if what they've served up will be enough to walk away with a win.