For the record, I don't think a Wii Sports U would create the same effect the original Wii Sports had since it's already been done and there's no "wow" effect anymore. Also it would be unfair to expect Nintendo to come up with something as huge as that phenomenon two times in a row.
I guess now we'll really see how effective Nintendo were at "converting" the non-gamers who bought the Wii to gamers. The sales of games like Mario Kart Wii and New Super Mario Bros. Wii seem to indicate it worked to some degree but I'm really anxious to see how it will hold up in the transition to Wii U.
@bolded: I completely agree.
I also agree that Nintendoland is not as quickly accessible as Wii Sports; just as the WiiU Gamepad is not as instantly intuitive as the Wii remote. However, I think there is more potential for longevity in both cases. Furthermore, we (supposedly) don't know all of the nuances of WiiU Gamepad details, nor do we know what the remaining minigames are in Nintendoland...
The fact is that WiiU will (likely) be $50 more than its predecessor and is being marketed more at the "core" gamers than at "casuals" when you look at most of the software. The reason that this is not a bad thing in my eyes is that first, there will easily be enough Nintendo fans looking to buy the system to make the launch/first months a success. And second, there is no reason that Nintendo can't broaden its mass-market appeal as the console comes down in price, since there is little threat from Durango or Orbis being able to match them on this level.