The genious of the Wii is that it is 100% BC. A new Wii could be the same -- there's lots of room for growth. A Wii HD won't kill off customers, it will give them the option to upgrade, just like the Wii did for the GC.
Nintendo could write a spec allowing devs to simply use allocate more texture space, etc. for games that want to work on both, but be nicer looking on the Wii HD. PC games have done that for eons.
Its like having a performance options panel where your console gets to decide how much to turn up the sliders. Since there would only be two settings, and it would be auto-set, not user tunable, this should be cake for devs to handle. Wii game == normal. You have a Wii HD? You get shadows, higher res textures, pixel shaders. Voila -- Wii for all.
Wii will be 1st, not last, because it is so succesful. Wii HD will not displace the Wii -- it will augment it. And it'll come in a zillion colors!
