I just
read about that yesterday. My feeling is that there will be a very small minority of Wii owners who will do this, much less than the 20% who are estimated to be online with the thing. But given the number of Wiis in the wild, that may still end up being a big enough number to be worthwhile to Netflix and Nintendo. The demographic is different, not as online-savvy as owners of the other consoles. Once they manage to get connected, they're going to have an appetite for content, and many won't know any better.
Here's an example that's very close to me. Sandy got her mother a Wii Fit and console for Christmas. I had to tell her the console wasn't included in the Wii Fit box. She ended up getting another such setup for herself. I set up the consoles at both houses, and immediately got them online through WiFi. Switched the router's channel from 6 to 1 because Nintendo can't get their online shit together except on a couple of specific wireless channels. Both consoles display on standard tube TVs (4:3 480i). When you go to the Nintendo channel (mostly advertising) it looks comparable to DVD on this setup. She couldn't care less about HDTV (although I did help her get a 19" Vizio for the kitchen recently, but that's another story). The tube TVs will be there until they die, and they both look great (for what they are).
She would be a prime candidate for streamed Netflix through Wii. She doesn't know or care much about options. She doesn't know a thing about games or consoles, or media centers. And if it works as well as it could (assuming the right tech people did their homework), it would look as good as anything on what she has.