This is exactly what I've been thinking of sense I first plugged the Wii into my 60" (and finally removed).
People always say upscaling does nothing but weather it's false image or not the quality will be upgraded. I'd like to get some comparisons of 480p and 1080p Zelda on that same tv. Not that it matters as my tv only hits 720p/1080i and I'd never blow that kind of money. If you're that desprete for HD you may as well just go with the real thing.
I do have one of those hd-dvd dvd-hd upscalers though and it looks great. Doesn't compare to full HD but there improovement from 420p is pretty great.
If a much cheaper Wii-specific upscaler comes out then I'd probobly jump on it. Pretty sure they have atleast 1 for the PS2.