I am not sure the masses are going to buy this a second time, we all know the masses have turned to the iPad and right now everyone is high on the iPhone 5 so the masses probably don't even know about this yet. Nintendo had a hit with the Wii because the price point was just right and it provided something different that was never seen before. Price is everything to get into the market in the US, or the masses might be saying, I am not going to drop $300 on this console, I already have a Wii that now sits here and collects dust. Now this is feeling more and more like a rehash. I also don't see the strong lineup of games, just another Mario game, and Nintendo land (which will almost surely drop in price quickly 2 years after the Wii U releases), there is nothing with mass casual appeal like Wii sports.
If they want the hardcore they have already lost them to Sony and MS. The truly die hards will pick this up as an extra console to play alongside their PS3 and Xbox 360, while they save their money for the next iterations of those consoles.
As far as the controller most people who want a tablet probably already have one, so they will dismiss this as a gimmicky attempt at trying to get into the marketplace.
Will this sell, I am sure it will sell during the holiday season, it is a new product after all, and there will be die hard fans that will buy it. The households that have everything will buy it because it is something they do not have. Will it keep selling after the initial holiday rush.. I have no idea. My guess is they pull the same thing they did with the 3DS, price it high to lure the die hards and the early adopters then when sales start slumping in march they will reduce the price to lure the rest of the people who did not pick it up yet. They will have to drop the price if this thing does not sell, or else they will have a failure on their hands.
There are still a lot of unanswered questions about this console (still waiting for battery life results of the controller, which I probably won't get until its been in the public's hands for a month)...
Another thing is a games console should be for games, I don't see a lot of games coming out for this system that I can't already get on one of my other systems, which are far superior to this and have tons of storage space, so much that I will probably never have to worry about using it all up. I am a big fan of Sony's PS Plus right now, I can't see a better value than paying $50 per year and getting to download a ton of free games.