Oh, I don't think it will be the only thing - the point I was trying to make (probably not at all clearly) is that for a huge group of people Wii (or more accurately, Nintendo) games in HD are going to be a big draw.
Remember, in many ways Nintendo haven't leapt into what many gamers consider "next-gen" yet (persistent online profiles, friends networks, DLC, HD etc.) so if their next console ticked a lot of those boxes, as well as adding a few new twists it could be quite compelling.
A Wii2 running at 1080p, with a solid online component, a more orthodox architecture, refined motion control and Nintendo taking a core-games-first approach? Not a bad proposition, especially if they could manage to leverage early support from third parties.
They're unlikely to be able to harness lightning two times in a row, but I could certainly see them shooting for something on top of the above, but I think as a base it's what we should be expecting.