If you really believe it, keep it in your sig until a month after E3.

Could they come up with an attachment that you plug the Wii's video output signal cord into and then it converts it into an hd signal?

I don't think it matters if it's possible or feasible to do it. You still haven't explained why Nintendo would bother doing this. It just doesn't make good business sense to do so, and without a simple reason that pertains to dollar signs, why would Nintendo do such a thing? It's nice to think about, kinda like how people love conjuring up conspiracy theories that don't have sound reasonings and are always more convoluted and ridiculous than real life tends to be, but that doesn't make it a sound prediction.

You mean like an upscaler.

Most HDTVs already have upscaling in them.... all an upscaler does is to help stop compatibility problems between SD and HD signals.... so it could help some HDTVs to stop it looking worse than it does on an SDTV.

At the moment, The Wii does look better [than SD] on most HDTVs if you buy the correct cables and set it up properly.... but there are some TVs that have issues or are difficult to set up correctly, and so sometimes things like jaggies can be abnormally more noticable.

Generally though that can be fixed by messing around with the TV settings, or if you haven't bought them, to use the component cables.

Haha.

What would support upgrading the Wii hardware, is the low demand in Japan.

And what is against the upgrade is:
Wii is selling faster than any home console so far.
Release of WM+ (that may boost the demand in Japan).
New use of SD cards.
No new colours yet.
No new bundles yet.
No pricecut yet.
Rumours about Wii interiors going 65nm.
More expensive hardware would eat the bottom line.

Nintendo propably didn't talk about Wii games much for:
GDC is game developers conference, not gamers expo.
DSi is Nintendos latest hardware, that they want to promote.
Nintendo wants to save the "big news" into E3 (that should be expo this year instead of press conference what it has been last two years).

This. 

Girls love the boys who have ridiculous predictions in their signature! 

     Because of the low sales in Japan previously mentioned as well as the fact that several sources have already announced that Nintendo has been looking at ways to make the Wii HD and Nintendo hasn't denied these reports.  Miyamoto even said they were looking into ways to do it.

http://blog.wired.com/gadgets/2008/10/next-for-ninten.html

"Some analysts have already expressed their expectations about high-definition version of Wii game console. However, they expected it to arrive in 2009 or 2010 did not anticipated them to be truly revolutionary."

http://www.xbitlabs.com/news/multimedia/display/20081002132103_Nintendo_s_Wii_HD_to_Is_Prepared_for_Launch_by_2011__Rumours.html

http://www.nintendorevolution.ca/11102008/12/nintendos_shigeru_miyamoto_talks_wii_hd

Nintendo always does things like this.  They make a few tweaks to their consoles so that they phase out the old one and give it price cuts while letting the new version justify keeping or adding a little bit to the old price.

Another example of them phasing out a highly popular console after it had only been on the market a short time = GBC to GBA.

that is one of the worts predictions ever

@BTFeather: First, when talking about WiiHD, we essentially are talking about an upgrade to the existing Wii platform. Why aren't we talking about WiiBD, a Wii with a BD drive build in, or WiiToaster, a Wii with a toaster built in, aswell. Not about the successor of Wii, that is pretty much guaranteed to launch 2011-2013.

Secondly, it shouldn't surprise anyone that Nintendo is working on their next console, call it a Wii 2 or N6 (it's likely not going to be named as Wii 2). Nintendo themselves have told us that developing a console is a process that never stops, once one is out, you start developing the next one.

Thirdly, Shigeru Miyamotos statements where he isn't really saying anything or random bloggers thoughts or what Pachter thinks doesn't really qualify as a proof.

Fourthly, with a 2011-2013 launch window, you really need to start talking to developers around these times, especially if you want to hear what the 3rd parties needs are considering the console.

Fifthly, the situation in Japan doesn't require the release of new console, or upgrade the old one before WM+, new colours and the current SD card feature have showed their effect. I believe Nintendo had already launched new colours in Japan if the supply hadn't been an issue.

If anything I think the Wii will have the longest life span. It makes absolutely 0 sense to make any changes while they are still at the peak of their consoles life.

I think everyone is looking at it probably being a longer console generation overall, but if past Nintendo consoles are any indicator they use a 5 year lifespan SNES (1991), N64 (1996), Gamecube (2001), Wii (2006) or other extremely successful consoles PS1 (1995), PS2 (2000) then they milked out an extra year and released PS3 in 2006 and look what happened.
I think realistically we should see the next nintendo console released in 2011.