With average generational growth of SW and HW I am going to say 10+.

Of the games currently available...
I'll say two...
Of future titles...
Nintendo Land 2...
I'm quite confident there will be a sequel...
And maybe Wonderful 101, but that's if they choose to aggressively promote it...
It looks charming, and I think it has the potential to sell well...
If they want to make it happen...

5-6 games should easily do it.

The Wiimote was something both A) new and exciting and B) immediately understandable to all people, gamers or not.

The gamepad is neither new and exciting (2nd touch screen is 8 years old now) and with a return to dual analog, the controller is not immediately understandable, despite having a limited touchscreen.

Furthermore, Wii's audience has largely moved to Kinect or moreover tablets.   To go from Wiimote to kinect to gamepad is completely illogical - if that's your idea of gaming then the dual analog, gamepad is a dinosaur.   However the hundreds of millions using smartphone and tablets for gaming are the bigger concern.

33% of all smartphone use and 65% of all tablet use is gaming.  When you think about it, that's an immense amount.  That's a higher percentage of time than my Wii gets (thanks to Netflix).  Tablets are primarily gaming systems and they outsell home consoles easily.   This is largely WiiU's audience now playing very simple games like Angry Birds, Fruit Ninja and such which used to play Wii Sports and Mario Kart.  Plus they are paying $0-$15 for a game.   Are they now going to go back to paying $60?   It's possible, but the game has to be a lot more enticing than what we're currently seeing on WiiU.

On the other end of the spectrum WiiU doesn't offer nearly enough to convince core gamers to buy it and buy games for it instead of just sticking to their existing HD system.  Plus we know the next gen systems for MS and Sony are on the horizon so most will wait to see what they offer.

From what we're seen so far, PS4 will still largely target the core - a losing strategy IMO - however MS is going to be very, very aggressive about casuals (and core).  A much enhanced Kinect along with halograms or other virtual reality tricks will make the Nextbox the most hyped gaming system since Wii.  IF those rumours and leaks have merit.  If MS can deliver a Wii Sports like killer game.  I'm not convinced MS has the DNA but they have had a couple solid years with Kinect to learn the ropes.  I don't think they'll totally drop the ball either.

Add in wildcards like Wikipad, Ouya, Oculus Rift and Steambox and WiiU is facing a degree of competition for both the core and casual that Wii never had.

Nintendo abandoned the dual screen idea for Wii and resurrecting it 6 years later doesn't make it more relevant.  In many ways it's seems primative compared to the touchscreen devices we already all own.   It is somewhat novel and I'm sure fun.  But so is Angry Birds.   WiiU fails to create a compelling reason to own it for most people.   Especially if you already own a Wii with NSMBWii, Mario Kart Wii, Wii Fit, etc.  The WiiU versions don't look to add enough to justify a new console and new game purchase for casual gamers.   If WiiU had launched in 2010, it would have benefitted more from the uniqueness of the controller (then) and the slip-over enthusiasm from the Wii.   But the Wii's shine started ebbing in 2009 and by 2012 there's little left over.

So this leaves the Nintendo core, enthusiast gamers who buy all consoles and whatever remains of Wii spillover.   I give WiiU the same sales as GC for the former and an extra 20m for the latter - minus 10m as I expect the home console market as a whole to shrink massively.   WiiU will also have all the challenges Wii and Nintendo always face (poor 3rd party support, sopratic game release, Nintendo's split attention between core/casual) but also the perks (Nintendo IPs and outstanding quality games)

30m is not a failure for Nintendo, especially because every WiiU + game sold is a profit, but it's no Wii success.   It will be disappointing but good enough considering the market shrinkage and competition.  It also allows Nintendo to launch yet another system in 4-5 years that will out-perform and out-innovate whatever MS/Sony had launched just 2-3 years earlier.

Way too early to think. Depends what kind of gamers will be on the console this gen, how much it selss, whether 3rd party do make an effort, and whether 1st party titles are successful. Let's wait till the Wii U actually hits 10 million units before we start predicting stuff that are unpredictable

I'm among the minority that actually thinks the Wii U will be bigger than Wii. If it gets continued 3rd party support, it could become THE system to play on, like the DS is (was?) for portables. It is going to dominate Japan. Obviously Super Mario Bros. U and NintendoLand are going to hit 10 mil. I think there will be many others. Games like Wii Fit U, Mario Kart, 3D Mario, Smash Bros seem like obvious huge games. I think you could also see the next Zelda being big. I think the "NEW" team is either going to release another Mario Bros (contrary to Nintendo remarks on there being one per system... there is just too much time before Wii U is done for them not to put out another) or NEW Zelda. Another 10 mil seller. I also think that some of the big games are going to be ones we haven't heard of or thought of yet. Nintendo is going to launch some new games that use the gamepad and appeal to the mass market and push the Wii U in 2013. Who knows what they will be, but they will be big and your girlfriend/wife/mom will love them. Then there is the possibility of big 3rd Party games. Monster Hunter U. Final Fantasy U. Future Call of Duties or GTA's. If Wii U sells enough, those kinds of titles could sell 10 mil, especially if they are ones that are big in Japan, where Wii U won't be competing with XBox. I don't know a number, but I'll say there will be more 10 mill sellers than on wii.. so at least 10.

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u should ask how many will break 20million.

How about 30m?  I'm going for 3

Why don't you have a poll for this thread spurge?

Five of them seems plausible, even if the Wii U ends up selling less than the Wii (I think it will, by a wide margin), Nintendo software has wings and rockets up their asses and seem to move without air resistance. There simply is no comparison in the gaming world today.
If the software is good enough, I wouldn't be entirely shocked if the Wii U managed as many 10 million sellers as the Wii despite a (probably) smaller userbase.