Not even commenting if your argument is right or wrong, but using sequential iPhone models isn't a great example to compare Wii's.
1st off, not all the people are going to know 3Gs is a successor to 3G, they're just going to think the S is a premium model of the 3G, and in alot of cases, they're not wrong.
2nd off, something like Xbox or even Playstation is far more easier to figure out, because to non-Nintendo owners, a new name generally means new system.
With Nintendo, they take one system, and give that system several revisions, but is still the same system.
Gameboy, Gameboy Pocket, Gameboy Color
Gameboy Advance, Gameboy Advance SP, Gameboy Advance Micro
Nintendo DS, Nintendo DS Lite, Nintendo DSi, Nintendo DSi XL
Nintendo 3DS, Nintendo 3DS XL, Nintendo 2DS.
To anyone familiar with the name Nintendo, but not the system could just assume all the Gameboy and Gameboy Advance brand are all one in the same and NDS and 3DS are all one in the same.
They just might assume Wii U is just a revision of Wii if they don't understand that sequential systems are described as generations.
Meanwhile to people that don't game can use common sense that Playstation and Playstation 2, or Roku and Roku 2 are different things.
Its safe to assume that the Wii was the 1st and only console to be owned by alot of people that don't normally play games, but were impressed by a modest tech demo. My father bought a Wii after playing one at a mall and for 7 fucking years all he had/owned was Wii Sports. Its that kind of person right there that made the Wii sell like hottcakes in its 1st 3 years. So when the Wii U comes out, that section of Wii owners aren't going to know what the F is a Wii U, and would likely not be interested. A large portion of Wii owners weren't gamers, and aren't going to be impressed or curious about new gaming technologies.