The Wii's standard definition graphics are part of the reason that the casual/core divide is there is in the first place, says Nintendo.
Plenty of gamers - probably a few too many - write the Wii off as a "casual only" console, but Nintendo is confident that the Wii U will not suffer the same fate. Shigeru Miyamoto thinks that the Wii U's extra graphical power will put Nintendo back on the hardcore gaming map, as Nintendo will no longer be left out of third party releases.
Miyamoto thought that Nintendo's decision not support high definition graphics on the Wii had, at least in part, been responsible for the separation between casual and core gamers. He said that there had been other factors, like controllers and the Wii's less than amazing online functionality, but that visuals were the element that people understood the best.
Obviously, he didn't think that the Wii really was just a casual console - adding that series like Legend of Zelda, which had always been designed with core gamers in mind, attested to that - but said that the updated graphics would help people get over the psychological hurdle. Nintendo boss Satoru Iwata also noted that being able to get a wider range of third party titles - something that was difficult to do on the relatively underpowered Wii - would help a great deal as well.
Miyamoto makes an interesting point; as much as people might claim otherwise, visuals do make a difference to how people perceive games. There are a lot of great games on the Wii, but as Iwata suggests, a lot of the really third party big franchises either skipped over the Wii entirely, or delivered inferior versions when compared to the Xbox 360 or PS3. Of course, Nintendo's marketing campaigns, which emphasized how easy it was for total novices to start playing, also played a big part in putting the idea that the Wii was a casual machine in people's head, and that's something that Nintendo will have to address in the future.