I think that it may not be necessary for current Wii owners to buy another Wii for HD. If you look at computers (or the PS2 or the Xbox, for that matter) it's not that the Wii is incapable of producing HD resolutions. It may simply a matter of updating drivers, which could be done via online update.
When the HD craze started hitting hard, I had old nVidia drivers which could not support 16:9 resolutions, but to fix that all I had to do was to go to the website, download the latest drivers and presto! 16:9 HD was mine to keep.
Why can't the Wii, or indeed, any console be able to do this?
Look at the PS2 with 1080i GT4, or the slew of 720p/1080i games out for the original Xbox. They didn't even require driver updates or patches. The game took care of that. Suggesting that the Wii is somehow incapable of accomplishing the same would mean Nintendo intentionally locked the resolution to the ATi GPU and threw the HD code out the window (and would also mean Nintendo did something astronomically stoopid).
"Plus Nintendo has to figure it won't be long now before the copycat giants introduce motion sensing controls of their own, and have ports of motion sensing thrid party Wii games with better graphics. It would do them well to catch up. And the system is cheap enough where it shouldn't be too much of an issue."
True true, but there is one fundamental difference: Said copycat giants would be releasing peripherals that are not integral to their respective systems, and historically it's shown that peripherals don't tend to sell very well. If it wasn't there to start with, chances are it won't last the distance.
"It wold be like the DS Lite to DS."
Not really. The DS Lite to DS is mainly in the exterior casing and screen, but their resolutions remain the same and apart from being more portable, there are absolutely no gameplay differences. Having HD when you didn't before, or having motion sensing (on the Wii's level or better) when you didn't before is a sizable change of direction, IMHO.
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